Why Prophet Muhammad Led Prophets in Prayer in Al-Isra’
Question

What is the reason why the Prophet Muhammad (peace and blessings of Allah be upon him) led the other prophets in prayer on the night of the Isra’? What does this indicate?
Praise be to Allah.The reason why the Prophet (peace and blessings of Allah be upon him) was made to go forward to lead the other prophets in prayer in Al-Masjid Al-Aqsa, which is the home of the prophets from Ibrahim Al-Khalil (peace be upon him) is that our Prophet Muhammad (peace and blessings of Allah be upon him) is the greatest leader, as was stated by Al-Hafiz Ibn Kathir (may Allah have mercy on him) at the beginning of his commentary on Surat Al-Isra’. 
He also said, when discussing how the Prophet (peace and blessings of Allah be upon him) led the other prophets in prayer: “Then his honourable status and superiority to them was manifested when he was made to go forward to lead them in prayer, when Jibril (peace be upon him) indicated to him that he should do so.” 
Undoubtedly our Prophet (peace and blessings of Allah be upon him) is the foremost among the prophets. He (peace and blessings of Allah be upon him) said: “I will be the leader of the sons of Adam on the Day of Resurrection and the first for whom the grave will be opened and the first to intercede and the first whose intercession will be accepted.” (Narrated by Muslim, 2278) 
One of the scholars suggested another reason why he (peace and blessings of Allah be upon him) was made to go forward to lead the prophets in prayer. He said: The Prophet’s words, “I led them (in prayer)” indicate – and Allah knows best – that this ummah took over the position of leading mankind.  
For more details about Al-Isra’ and Al-Mi`raj, please see the following answers: 60288 , 84314 , 11086 , 203789 , and 105456 .
And Allah knows best.