Sorry for the delay, guys — Fridays are nights of fun and frolicking in the _Theman household, lol;
This period of time isn’t my expertise, but basically Carter came across as very much the ally of the Shah but then expressed support for Khomeini (yes, this actually happened once upon a time). This pissed off the Shah’s supporters and undercut his base of power. Then, when things were getting messy and US allegiance switched back to the Shah, he (well, the US) provided safe harbor for him and refused to turn him over to Khomeini. All of this pissed off Khomeini’s supporters.
So depending on whose side an Iranian was on back then, Carter could be viewed as a backstabber who shouldn’t be trusted (as if any should?) and either decided the outcome of the revolution (by backstabbing the Shah) or caused it to go on even longer and be more bloody (by then supporting the Shah) and not allowing for “justice” to be done.
EDIT - so the Iranians didn’t have any designs for the hostages, but they certainly worked as leverage and they knew it was terrible optics for Carter. Despite claims that they feared Reagan, my understanding is that the freeing of the hostages was a done deal as soon as Carter was gone, regardless of who sat in the Oval Office.
EDIT #2 - just to clarify something: I actually liked Carter, despite a few obvious shortcomings of his administration on the international stage and in the Middle East. I’d argue he was one of the more truly decent people to hold the office. I just wish he was better at it.