The leftists allied with the religious nutjobs in the revolution, then got murdered immediately afterwards because the religious nutjobs didn’t want a leftist government that tolerated religion, they wanted an authoritarian theocracy. Some people somehow think that any leftist-backed revolution always goes brilliantly and ends up with utopian socialism or communism and no one ever exploits the post-revolutionary power vacuum for their own ends. That isn’t compatible with what happened, so instead, they must believe that the leftists survived being murdered and now run Iran.