The ayatollahs got into control because the Shah used them to overthrow the parliament (Behbahani and Falsafi and finally Kashani), used them to attack the left

The ayatollahs got into control because the Shah used them to overthrow the parliament (Behbahani and Falsafi and finally Kashani), used them to attack the left etc. In fact, as I mentioned in another post, one of their first acts (1955) were the Shah and Falsafi conspiring to start an anti-Bahai campaign which caused riots which killed Bahai. The US and shah and Savak did too well stamping out secularism, left-wing ideas, even liberal ideas about parliament, democracy etc. Eventually the ayatollahs and Bazaari etc. amassed great power, and turned on the Shah. Mossadegh was never in the pocket of the ayatollahs, but he did try to qualm moderates like Kashani. But Kashani eventually turned on him (the hard-line preachers had far before).