A lot of the stuff that Khomeini promised never ended up coming to fruition. It’s actually somewhat ironic as a lot of the tape recordings of his original speeches are now banned from being distributed since a lot of the stuff he promised he didn’t deliver.

The public wanted the Shah out, and while the Shah himself loved the country, his inner circle was corrupt and the focus was so much on modernizing that only major urban centers like Tehran and Shiraz were getting the focus, many rural areas were in such bad shape they weren’t even able to get everyday necessary supplies. Of course the corrupt circle was skimming off the top at the same time.

So you got a bunch of pissed off people from rural parts of the country, they are religious and you got Khomeini promising a bunch of government subsidies and well things start to turn sour. In addition, the Shah ended up getting his military upset at him in scenarios where he was using his military for stuff that upset his troops. For example, an Iranian helicopter pilot (who later died in the Iran-Iraq war and is a martyr considering the missions he volunteered for) interviewed later saying how he was trained to be a military helicopter pilot but during the 2500 year celebration of the Persian empire that the Shah organized at Persepolis, they had the pilot ferrying rice and cooking supplies back and forth from Tehran to Shiraz. Who knows if it’s true or not but again, people were upset, Shah was throwing lavish parties and households were hungry, Khomeini was promising free stuff in abundance, and here we are.