Who put abbaside in power , who were the power behind the scene and who were the ones who changed the caliph whenever they wanted and who defeated the caliph and made him their own vessels .
Abbaside Chalifate were nothing but puppets in the hand of non Arabs . now if your history say something else honestly that's not my problem .
In short some people needed puppets in power and those puppets must had relation to the Holy prophet and so come abbaside dynasty.
At least imagine come to power by their own means and cunning but what about abbaside ?