AskHistorians

The issue of whether the Iranian hostages were intentionally held is still debated. I believe it, but it's still not settled fact.

The Iranian government itself was far from united at this point - hence why one of the accusers of the October Surprise Theory is the Iranian president of the time, who asserts that Ayatollah Khomeini and the Islamic hardliners in the government struck the deal with Reagan.

Yes, because Carter was willing to interact with Iran like any other country. Sometimes that meant hostility - as with the failed hostage rescue attempt earlier in 1980. But oftentimes, that meant negotiating and finding common ground - something which may have been found with the left-wing elements of the Iran Revolution, but unlikely to be found with the Islamist hardliners. In other words, Carter might have supported the Islamists' domestic rivals. Reagan, by contrast, promised (implicitly) to give the Islamists the siege-state they needed to rally support, and would never have offered support to even mild left-wing elements. Both Reagan and the Islamists saw a convenient enemy in the other - and neither gave a fuck what price the Iranian people might pay so the two could get their rocks off playing nationalist-theocrat dick-measuring contests on the international stage.

Because Reagan was a shitbag without any morals or loyalties.