People will say "Mosaddegh was himself a dictator!!!", even though this claim is only partially true at best.
He was elected, and was very popular with the people. He was forced out by the conservative Shah but then reinstated when the Shah realized that he was simply too well-liked.
He was secular, leftwing, even liberal, and not a religious fundamentalist. He was attacked by the Shia fundamentalists (future Khameneists) for being a "Communist" (irony).
He assumed "dictatorial powers" in order to push through his policies that actually favored the Iranian people. This is what led to the coup against him (sponsored by the U.S. and Britain).
This coup brought the repressive dictatorial Sha to power, whose repression led to the 1979 Revolution which led to what we see today.
Every horror that Iran has inflicted upon the Middle East and every horror that has been inflicted upon them could have been prevented if, in the 1950's, democracy was given a chance in Iran.