> But isnt that exactly what happened in 1979?
No, what happened in 1979 was the reversal of the previous overthrow of their government.
The reason it’s an Islamic government is because the puppet we installed destroyed their civil society and the mosques were the only place where any resistance to the imposed despotism could congeal.
Domestic overthrow of the mullahs would ideally restore what MI6 and the CIA screwed up back in 1953 - representative, legitimate, secular government.
Had the Soviets gained access to Iranian ports and of course the critical chokepoint of the Straits of Hormuz, the West would have been effectively cut off from most of our sources of oil. Oil is crucial in time of war, and this was an unacceptable risk to the West.
Mosaddegh's overthrow didn't cause Khomenei: the Shah and Savak - and a weak President - caused Khomenei.