Why doesn’t Allaah hasten the destruction of the kuffaar? Why are the Muslims backward?
Question

Why doesn’t Allaah punish the Christians and Jews? Why are the Muslims so backward when the Christians and Jews are progressing?.
Praise be to Allah.Firstly: 
Perhaps what the questioner means by destruction is punishment and doom, because punishment is more general in meaning that destruction. Allaah punishes the kuffaar for their kufr with a hard life and darkness in the heart and hard-heartedness. What we see of them living a good life with fine food, clothing and houses is only outward appearances and does not reflect what is really in their hearts. The same applies to sinners as well as kaafirs. 
With regard to the delay in punishment and destruction of those who disbelieve in Allaah, Allaah has mentioned many reasons for that in His Book, for example: 
1 – Allaah, may He be glorified and exalted, is Oft-Forgiving and Most Merciful, and he delays their destruction so that they might repent and become Muslim. 
Allaah says (interpretation of the meaning): 
“And your Lord is Most Forgiving, Owner of mercy. Were He to call them to account for what they have earned, then surely, He would have hastened their punishment”
[al-Kahf 18:58]
Imam al-Tabari (may Allaah have mercy on him) said: 
Allaah says to His Prophet Muhammad (peace and blessings of Allaah be upon him): O Muhammad, your Lord is the Concealer who covers the sins of His slaves with His pardon if they repent from them.  
“Owner of mercy. Were He to call them to account for what they have earned” i.e., those who turn away from His signs, when they are reminded of what they have earned of sin. 
“then surely, He would have hastened their punishment” but by His mercy towards His creation He does not do that until their appointed time comes. 
Tafseer al-Tabari (18/52). 
2 – One of the attributes of Allaah is forbearance, and one of His beautiful names is al-Haleem (the Forbearing). So He does not hasten the punishment, rather He grants His creation a respite without ignoring their deeds, but He does not fail to punish them when He wills.  
(a)al-Shaykh al-Shanqeeti (may Allaah have mercy on him) said:
Allaah says (interpretation of the meaning): 
“Were He to call them to account for what they have earned, then surely, He would have hastened their punishment”
[al-Kahf 18:58]
In this verse Allaah explains that if He were to call people to account for what they have earned of sin, such as kufr and disobedience, He would have hastened their punishment, because of the abhorrent nature of their deeds, but He is forbearing and does not hasten the punishment, so He grants them respite but does not ignore their deeds.  
Adwa’ al-Bayaan, 4/164 
(b)and he (may Allaah have mercy on him) said, commenting on the verse (interpretation of the meaning):
“And if Allaah were to seize mankind for their wrongdoing, He would not leave on it (the earth) a single moving (living) creature, but He postpones them for an appointed term and when their term comes, neither can they delay nor can they advance it an hour (or a moment)”
[al-Nahl 16:61]: 
In this verse Allaah says that if He were to hasten the punishment for mankind, He would destroy everyone who is on earth, but He is forbearing and does not hasten the punishment, because hastening is the action of one who fears missing an opportunity, and the Lord of the heavens and the earth does not miss anything that He wills. 
This is mentioned in more than one place, such as the verse at the end of Soorat Faatir (interpretation of the meaning): 
“And if Allaah were to punish men for that which they earned, He would not leave a moving (living) creature on the surface of the earth; but He gives them respite to an appointed term, and when their term comes, then verily, Allaah is Ever All‑Seer of His slaves”
[Faatir 35:45]
And in the verse: 
“And your Lord is Most Forgiving, Owner of mercy. Were He to call them to account for what they have earned, then surely, He would have hastened their punishment. But they have their appointed time, beyond which they will find no escape”
[al-Kahf 18:58]
Adwa’ al-Bayaan (3/263) 
3 – The punishment of the kuffaar will undoubtedly come to pass in the Hereafter, and the delay therein is only because the time decreed by Allaah has not yet come, which is the Day of Resurrection. 
Allaah says (interpretation of the meaning): 
“and had it not been for a Word that had gone forth before from your Lord, the case would have been judged between them, and indeed they are in grave doubt concerning it (this Qur’aan)”
[Hood 11:110]
“And had it not been for a Word that went forth before from your Lord, and a term determined, (their punishment) must necessarily have come (in this world)”
[Ta-Ha 20:129]
“And your Lord is Most Forgiving, Owner of mercy. Were He to call them to account for what they have earned, then surely, He would have hastened their punishment. But they have their appointed time, beyond which they will find no escape”
[al-Kahf 18:58]
“Consider not that Allaah is unaware of that which the Zaalimoon (polytheists, wrongdoers) do, but He gives them respite up to a Day when the eyes will stare in horror”
[Ibraaheem 14:42]
(a) al-Baghawi (may Allaah have mercy on him) said:  
“And had it not been for a Word that went forth before from your Lord, and a term determined” [Ta-Ha 20:129]. What this means is that were it not for a word that went forth before from your Lord, it would have been binding and a term determined. The word is the ruling that the punishment be delayed for them, i.e., were it not that it had previously been decreed that the punishment should be delayed for them. And the phrase “a term determined” refers to the Day of Judgement. 
“(their punishment) must necessarily have come (in this world)” the punishment would inevitably have befallen, as happened to the kuffaar in the past. 
Tafseer al-Baghawi (5/302) 
(b) Ibn Katheer (may Allaah have mercy on him) said: 
Allaah says (interpretation of the meaning): “And had it not been for a Word that went forth before from your Lord, and a term determined” [Ta-Ha 20:129]. This means that were it not for a word that was previously issued by Allaah, stating that the reckoning for His slaves should wait until the Day of Resurrection, the punishment would have been hastened for them in this world.
Tafseer Ibn Katheer (7/195). 
(c)Shaykh al-Sa’di (may Allaah have mercy on him) said: “And had it not been for a Word that went forth before from your Lord,” to delay it and not hasten the punishment for them, “(their punishment) must necessarily have come (in this world)” the punishment would have come to the wrongdoers, but the wisdom of Allaah dictated that judgement between them should be delayed until the Day of Resurrection.
Tafseer al-Sa’di (p. 390) 
(d)al-Shanqeeti (may Allaah have mercy on him) said:
Allaah says (interpretation of the meaning): “But they have their appointed time, beyond which they will find no escape”[al-Kahf 18:58]. In this verse Allaah states that even though He does not punish them immediately, He is not ignoring them or failing to punish them, rather He has set an appointed time for them when He will punish them, and He will not delay the punishment beyond that time or bring it forward.  
Adwa’ al-Bayaan (4/164, 165). 
4 – With regard to those who are ungrateful for the blessings of their Lord, and do not turn to His mercy, and persist in their kufr and stubbornness, delaying the punishment increases their sin, until they meet their almighty and vengeful Lord with an abundance of sin, and they no longer have any excuse. 
Allaah says (interpretation of the meaning): 
“So think not that Allaah will fail to keep His Promise to His Messengers. Certainly, Allaah is All‑Mighty, All‑Able of Retribution”
[Ibraaheem 14:47] 
“And let not the disbelievers think that Our postponing of their punishment is good for them. We postpone the punishment only so that they may increase in sinfulness. And for them is a disgracing torment”
[Aal ‘Imraan 3:178] 
“So make no haste against them; We only count out to them a (limited) number (of the days of the life of this world and delay their term so that they may increase in evil and sins)”
[Maryam 19:84]
(a)Imam al-Tabari (may Allaah have mercy on him) said:
The meaning of the verse “We postpone the punishment only so that they may increase in sinfulness” [Aal ‘Imraan 3:178] is: We are only delaying the punishment and giving them a long time so that they may increase in sin.
 “And for them is a disgracing torment” means for those who disbelieved in Allaah and His Messenger, a punishment in the Hereafter that will be shaming and humiliating. 
Tafseer al-Tabari (7/423). 
(b)al-Tabari also said:
“So make no haste against them; We only count out to them a (limited) number (of the days of the life of this world and delay their term so that they may increase in evil and sins)” [Maryam 19:84] – here Allaah is saying: Do not hasten to seek punishment and destruction for these kuffaar, O Muhammad. 
“We only count out to them a (limited) number (of the days of the life of this world and delay their term so that they may increase in evil and sins)” means, We are only delaying their destruction so that they may increase in sin, and We are counting all their deeds, even the smallest of them, so that We may punish them for all of them, and We are not delaying their destruction for some good that We will for them. 
Tafseer al-Tabari (18/252) 
What a serious warning and what fear it instills in the heart; what grave vengeance and retribution, when the Compellor, the Sublime warns the rebellious sinner of what he deserves because of his sin, when there is no way out for him and nowhere for him to flee to. 
Al-Bukhaari (4686) and Muslim (2583) narrated that Abu Moosa said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Allaah, may He be glorified and exalted, grants respite to the wrongdoer, but when He seizes him He will not let him off.” Then he recited: “Such is the Seizure of your Lord when He seizes the (population of) towns while they are doing wrong. Verily, His Seizure is painful (and) severe” [Hood 11:102]. 
Secondly: 
With regard to the second matter which is the backwardness of the Muslims and the advancement of the kuffaar in the standard of living and worldly sciences, you should understand that their progress does not go beyond worldly matters. As for true knowledge, which is knowledge of Allaah and the Hereafter, they have no share of that. Allaah says (interpretation of the meaning): 
“They know only the outside appearance of the life of the world (i.e. the matters of their livelihood, like irrigating or sowing or reaping), and they are heedless of the Hereafter”
[al-Room 30:7]
This is also part of Allaah’s establishing proof against them, as He gives them the means that enable them to gain useful knowledge of that which will benefit them and guide them towards the true religion, but they allow themselves to be distracted by worldly matters and they do not benefit from it in such a way as to save themselves and set things straight for themselves in the Hereafter, and so that their worldly affairs would be set straight too.  Allaah says (interpretation of the meaning): 
“And indeed We had firmly established them with that wherewith We have not established you (O Quraysh)! And We had assigned them the (faculties of) hearing (ears), seeing (eyes), and hearts; but their hearing (ears), seeing (eyes), and their hearts availed them nothing since they used to deny the Ayaat (Allaah’s Prophets and their Prophethood, proofs, evidences, verses, signs, revelations, etc.) of Allaah, and they were completely encircled by that which they used to mock at!”
[al-Ahqaaf 46:26]
Hence Allaah says, forbidding His slaves to be deceived by what they have of worldly wealth and adornments: 
“Let not the free disposal (and affluence) of the disbelievers throughout the land deceive you.
197. A brief enjoyment; then, their ultimate abode is Hell; and worst indeed is that place for rest”
[Aal ‘Imraan 3:196, 197]
al-Shawkaani (may Allaah have mercy on him) said:  
“Let not the free disposal (and affluence) of the disbelievers throughout the land deceive you” – this is addressed to the Prophet (peace and blessings of Allaah be upon him), and is intended to urge him to remain steadfast, as in the verse “O you who believe! Believe” [al-Nisa’ 4:136], and it is also addressed to everyone. This verse speaks of the bad situation of the kuffaar after it speaks of the good situation of the believers. What it means is: do not be deceived by their free disposal throughout the land and their travelling for trade, which gives them an affluent standard of living, for it is brief enjoyment that they enjoy in this world, then their fate will be in Hell. It is brief enjoyment that is as nothing when compared to the reward of Allaah. 
“their ultimate abode” means, where they will end up. 
“their free disposal throughout the land” means their travelling to various places. This is like the verse in which Allaah says: “So let not their ability of going about here and there through the land (for their purposes) deceive you” [Ghaafir 40:4]. “Enjoyment” refers to that which they benefit from immediately, and it is called “brief” because it is transient and every transient thing, even if it is great, is in fact brief. 
“and worst indeed is that place for rest” refers to what they have prepared for themselves in Hell because of their kufr, or what Allaah has prepared for them in Hell.  
Fath al-Qadeer (1/622, 623) 
You should understand that Allaah has laid down natural laws for the development of the earth, to be able to make use of its resources and to benefit from what is in it and to attain the means of strength. These laws apply to all people. Whoever applies the means of strength will attain it, by the Leave of his Lord, but what matters is how to attain that in accordance with the laws prescribed by Allaah, and then use it in such a way that will help him and others to attain the pleasure of Allaah.  Allaah says (interpretation of the meaning): 
“Whoever desires the quick‑passing (transitory enjoyment of this world), We readily grant him what We will for whom We like. Then, afterwards, We have appointed for him Hell; he will burn therein disgraced and rejected ( far away from Allaah’s Mercy).
19. And whoever desires the Hereafter and strives for it, with the necessary effort due for it (i.e. does righteous deeds of Allaah’s obedience) while he is a believer (in the Oneness of Allaah Islâmic Monotheism) — then such are the ones whose striving shall be appreciated, (thanked and rewarded by Allaah).
20. On each - these as well as those- We bestow from the Bounties of your Lord. And the Bounties of your Lord can never be forbidden”
[al-Isra’ 17:18-20]
The wisdom of Allaah in making the means of living easy and making this world attractive to these kuffaar, is that whoever among them does something good will enjoy what he has in this world, as a reward for his good deeds, then when he meets his Lord on the Day of Resurrection, he will not have any hasanaat for which Allaah will reward him. 
It was narrated that Anas ibn Maalik said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Allaah does not treat the believer unjustly with regard to his good deeds. He blesses him because of them in this world and He will reward him for them in the Hereafter. As for the kaafir, he is fed because of the good deeds that he does for the sake of Allaah in this world, then when he passes on into the Hereafter, he will have no good deeds left for which to be rewarded.” Narrated by Muslim (2808). 
Hence Shaddaad ibn Aws (may Allaah be pleased with him) said: This world is transient and passing, in which both the righteous and the immoral eat. But the Hereafter is a true promise in which a stern Sovereign will pass judgement. Each of them has its sons, so be among the sons of the Hereafter and do not be among the sons of this world. 
Sifat al-Safwah (1/709). 
We should also point out here that this does not mean that the believers should refrain from pursuing the means of attaining strength that the kuffaar are enjoying and using to keep people from following the way of Allaah. Rather the believers are enjoined to develop the earth in accordance with the way prescribed by Allaah. Allaah says (interpretation of the meaning): 
“And to Thamood (people We sent) their brother Saalih (Saleh). He said: O my people! Worship Allaah: you have no other ilaah (god) but Him. He brought you forth from the earth and settled you therein, then ask forgiveness of Him and turn to Him in repentance. Certainly, my Lord is Near (to all by His Knowledge), Responsive”
[Hood 11:61]
Allaah has commanded His slaves to seek the means of attaining strength of all kinds when facing their enemies:  
“And make ready against them all you can of power, including steeds of war (tanks, planes, missiles, artillery) to threaten the enemy of Allaah and your enemy, and others besides whom, you may not know but whom Allaah does know”
[al-Anfaal 8:60]
Shaykh Ibn Sa’di (may Allaah have mercy on him) said: i.e., everything that you can muster, of intellectual and physical strength, all kinds of weapons and so on, which will help in fighting them. That includes all kinds of manufacturing of various types of weapons and means of defence, machine guns, bullets, aircraft, land and sea vessels, strongholds, trenches,  defensive weapons, and developing wisdom and policies that will help the Muslims to advance and ward off the evil of their enemies, and learn how to shoot, how to be brave and how to manage resources. Hence the Prophet (peace and blessings of Allaah be upon him) said: “Strength is shooting.” Narrated by Muslim (1917). 
That also includes preparing the vehicles that are needed when fighting. Hence Allaah says “including steeds of war to threaten the enemy of Allaah and your enemy”. This reason existed at that time, which was to scare the enemy and the ruling depends on that reason.  If there is something that could instil more fear in the enemy, such as land vehicles and aircraft which are prepared for fighting, then we are enjoined to prepare them and acquire them, and if we do not have them, then we should learn how to manufacture them. That is obligatory, because “that which is essential to fulfilling an obligatory duty is also obligatory.” 
See also the answer to question no. 33679 for information on some of the worries, distress and misery that affect the lives of the kuffaar.  
And Allaah knows best.