As with any revolution, a lot of factors - on the micro and macro scale - go into it. I’m not too knowledgeable about the economic status of Iran before the revolution, but the driving rhetoric behind the Iranian Revolution was a form of anti-Western, anti-imperialist ideology or sentiment.
As with any revolution, the current government wasn’t doing too well. The populace of Iran was becoming more and more convinced that the royal family didn’t truly represent the interests of the people, and were beholden to Western interests. Iranian oil was owned almost entirely by foreign nations, and a US/UK-backed coup d’etat occurred when Prime Minister Mosaddegh attempted to nationalize Iran’s oil reserves. And it’s easy to imagine how this sort of thing can create doubt about the legitimacy and loyalty of the government. In addition to all this worrying political and economic stuff, the Shah in charge at the time of the Revolution was becoming increasingly dictatorial. Imagine all the regular things when you hear something described as a “regime.”
Social policies which strove to enforce Western ideals of feminism and women’s rights show a disconnect between Iran’s ruling party and the lower classes. Higher and middle-class women enjoyed more freedoms under the Pahlavi government, but being a part of women’s associations and lobbying for policies is, by nature, not a lower-class pastime. The classic rhetoric says that while the higher classes were enamored with Western dress, music, books, etc., the lower classes stuck to their religious roots. Obviously there was more variation between people than that, but the Iranian revolution was a popular, Islamic movement. During some events, women were forcibly unveiled in the streets in hopes of emancipating them. However, many women lived in a social sphere where simply unveiling would not have done much for emancipation, and forced unveiling obviously didn’t take into account the woman’s own feelings on the matter - many women wore veils and full chadors to express their religious devotion.
By the time of the Revolution, Ayatollah Khomenei has spent over 15 years in exile for opposing the reign of the previous Shah. But he was a hugely popular and influential figure, with books and cassette tapes of him speaking circulating all over Iran. He promoted the idea that revolution was not only for political and practical means, but that it was also a religious and cultural fight against the West.
At its core, I would say the Iranian Revolution was a reaction to Western influence in the Middle East. It wasn’t unique in that sense, but it was one of the most intense reactions against Westernization in the area. For hundreds of years there has been a push-pull between the West and the East, where the West has been becoming increasingly dominant and the Middle East has had to deal with that fact. Many Arab and Muslim countries responded by embracing Westernization and everything that came with it (Turkey being one of the most famous), but the pendulum swung and Iran ended up taking the opposite route — to double down on its own traditions and live in the modern world without conforming to it.
It’s been a while since I wrote my paper on this so there’s a lot of gaps, but I hope I was helpful!