While I was in Iran in the 70s I (and many other) considered the only threat possibly strong enough to stage a violent large-scale revolution to be the communists/socialists.
There was already islamic terrorism since decades, but always quickly put down. Few did anticipate that black reaction, the Quran thumping turbans, would be capable of beating both the Monarchist/pro-Western forces and afterwards the Communists. 1979 was a rough awakening for the world, bringing Islamism as a global player into the forefront.
Aha. What’s behind the Iranian culture part of the question you asked is your own experience.
Were you in Iran/Azerbaijan during Aashura?