What did the umayyads do that the abbasids did not?

Answer 1

Under the Umayyads, Mawali (or non-Arab Muslims) were traditionally excluded from political and social affairs. The Umayyad rulers, in particular, treated them as second-class Muslims. The evidence of this treatment was that Mawali were not allowed to have many government positions and that they were taxed whereas Arab Muslims were not taxed at all. Mawali made up an important component of the Umayyad Caliphate, especially Persians. Persia was always a high seat of culture in the Islamic Empire. As a result, ideas moved quite freely throughout Persia and Persians considered themselves to be of equal worth to Arabs.

Conversely, under the Abbassids, consistently treated Mawalis like Persians equal to or better than their Arab brethren which created animosity and a sense of betrayal. Many Arabs saw the Persians as the major backers of the Caliphate and that they were a tool for Persian interests. It was also perceived that the Persians were first servants to the caliphs but climbed way up the social ladder to a place they did not belong.

Answer 2

The Umayyads established a centralized and hereditary system of rule, where power was concentrated in the hands of a few family members. On the other hand, the Abbasids introduced a more inclusive and merit-based approach to governance, where positions were open to a wider range of individuals based on their abilities rather than their familial ties. Additionally, the Abbasids shifted the capital from Damascus to Baghdad, signaling a change in the political and cultural center of the Islamic world.