OK, I will try. First, keep in mind that velayat-e faqih was only published in 1970. Khomeini was, to say the least, a household name before then. He symbolized, at the very least, the opposition of traditional religious elements to the shah. Many believed him to be the Mahdi, a messianic figure, a claim that Shah Ishmail I of the Safavids made 500 years ago, after forcibly converting the country to twelver Shia Islam. I would argue that the system of government gains legitimacy from Khomeini's role in creating it, and its "nativity". To my understanding, accepting Khomeini's system of government (to be clear, that is what velayat-e faqih is. It's not a school of theology) did not trigger some massive shift in peoples' religious beliefs.
The point I'm trying to make is that there's a widespread idea that Iran wasn't all that religious before the "revolution" (or coup, if you prefer). This is to a great degree due to propaganda by the the Pahlavi Shahs and other nationalists, and the fact that most Westerners were only really exposed to the very liberal, very propped-up and ostensibly prosperous Tehran. Meanwhile, it is notable that, for example, university attendance rates in the country was around 5% in the 60's and 70's, I believe, and most of those studied abroad. (Today it's something like 35%, the majority being women.) Iran was very non-urbanised, and the countryside was very religious and conservative.
Prior to the Pahlavi dynasty, the history of religious oppression in Iran is very long, arguably going back to pre-Islamic times, though to what degree there exists a continuity there is debatable. Indeed more freedom was allowed under that dynasty (unless you were a socialist) but the Pahlavis simply weren't all that popular. Most of Iran was very religious before them, continued to be under them, and continued to be after them. The idea that the BULK, including non-urban population, are only religious in the way they are due to constant oppression is based on a propaganda-inflicted misperception of Iran and its history.