The disintegration period of the Arab Caliphate?

The Arab Caliphate did not last long and had already disintegrated in the 7th century for a variety of reasons.
The real power of the Abbasids did not want to recognize the just the former government, which was brutally overthrown. Also, various contradictions were strengthened between peoples who had different points of view on Islam – these are Sunnis and Shiites. Also, the incumbent caliph gave too much freedom to his subordinates to suppress the Arab uprising. The environment warmed up the decay, as the Caliphate was mostly in a dead desert. A fairly substantial number of Seljuk Turks migrated to the huge Arab Caliphate.