Carter's real and lasting legacy is that is a naive fool whose wishes and biases caused him to do immensely stupid things.
In the case of Iran, it's an established fact that the Shah and his regime were not a particularly shining example of freedom and good behavior. And Carter saw that, and said "he must go," failing to consider what would replace him.
That sort of short-sighted feel-goodism was the hallmark of Carter's foreign policy -- it was repeated (and exploited by the Soviets) countless times in Asia, Africa, and South America.
The Shah was hated immensely in Iran and was going to fall eventually. However, Carter's naive stupidity took a bad situation and made it much, much worse by throwing everything into fast forward and giving Khomeini the opening he needed.
The entire Carter Administration was full of bumbling fools who had no business directing American domestic and foreign policy. We have been paying the price for their stupidity for the last 28 years.
As with almost any revolution, those who begin it usually end up dead, exiled, or supressed while another group comes in...hence, Khomeni.
The Shah made his major mistake by taking land from the Imams and giving it to the people. He also tried to drag the people into the 20th Century too fast. He built his people good roads, hospitals with free care, gave them free eduction. It's my belief that Carter is a marxist idiot who also fawns over any murderous dictator that he can find.
Remember when Carter was going to give one of his fireside chats and an aide lamented that Carter spent 2 hours or so trying to decide which sweater to wear but only spent about 15 minutes on the speech?
Remember when businesses had to have their thermostats on at a certain degree or they'd be heavily fined? A lot of businesses started putting locks on their thermostats at that point. I was working at a restaurant at the time and thought it was ludicrous.
Misery Index? Malaise?
I read where Carter turned on the Shah because the Shah wouldn't pay a $100,000 bribe (that's basically what it was) to some of Carter's buddies.
Carter had alot of people fooled because he "appeared" to be a moral, good person...in a Machiavellian way but I believe that was just an appearance.
He is a failed prince who couldn't keep power and did everything wrong except his appearance of being a good, moral person on the surface. Dig deeper and you find him rumored by people who actually know him and worked with him to be a small, petty, vindictive, little man.