Why are there so many different paths? I will admit I am just starting to look into buddhism and such. I am confused because so far I understand that the Satipatthana sutta provides everything anyone needs to become 'enlightened'. 

If that is the case, then why is there so many different forms of buddhism (including the tantric one) each with various meditation techniques etc? If the Satipatthana sutta (or Anapanasati sutta) are the 'bread and butter' of buddhism, why would anyone need anything else/different to achieve their enlightenment?

Its like, if something works then why even bother changing it up?
This problem is not only with buddhism ,rather with almost every religion.  

During his time , Buddha never taught any tantra , mantra or yantra. Although his teachings vary from person to person but with common as 5 Percepts , cycle of suffering , impermanence &amp; eight fold noble path. Satipatthana sutta came later for intelligent beings. There were people who wouldn't understand any meditation, buddha used to teach them karma path, eg.,  'truth' is  to be loved - for newly married couples  ,...

Even during buddha's time , few people didn't need any meditation as they remain aware every moment residing nearby him ,like Ananda. Even animals used to move towards awareness ,eg., drunk elephant bowed in front of buddha , lion wouldn't kill anyone near enlightened one. 

Rise of tantra , mantra , yantra in buddhism was due to incapability(less power) of truth_seekers after buddha to remove bad omen from atmosphere just by upadesh(lessons) via voice &amp; hence leading to basic teachings to be insufficient ,especially in Himalayas where to keep body warm , people were dependent on alcoholic_foods making them completely ineligible for basic teachings. That's where , Hindu Aghori teaching of tantra , mantra &amp; yantra was mixed with basic teachings to generate a new teaching of Mahayana ,Vajrayana ,Tantrayana etc. with common as 5 Percepts , 8 fold noble path , cycle of suffering &amp; impermanence. 

Why buddha didn't teach tantra ,mantra or yantra?
     Because , these come under powers(Siddhis) and powers are merely used for fulfilling one's desire. This increases &amp; gives more space for Ignorance.  

When you are stuck in problem and haven't won your fear , you will definitely try to use powers to get out of that problem. This is the main reason behind power in buddhism , hinduism , Christian(white magic) etc...