Freedom of thought and despotism in Islamic history

In the introduction to his book, Shakib Arslan presents a general view of the history of Islam. This is the author's thesis. It needs to be compared with works on the history of theology and politics, and not all historians accept it. ¹

Arslan sees an early age, governed by independent reasoning (ijtihad) and intellectual freedom. Then the caliphate turned from consultation into despotism, so intellectual freedom receded, and transmission and imitation came to prevail over reason. ¹

He says that the Mu'tazila arose in an atmosphere of intellectual freedom, but when they acquired a political influence some Umayyad caliphs feared them and fought them. He then says that the people of the Sunna and transmission later prevailed, and he counts this shift as part of the history of despotism in the East. ¹

The source of the information is a single one. The author's claim that the Umayyads fought the Mu'tazila for political reasons needs a further modern source.