I’m not defending Carter or the Iranian Revolution, but in 1979 the Shah was dying and there was no legitimate successor to the Shah who could have held on to power.
Short of the U.S. Military occupying Iran to prop up the next Shah, thus causing nuclear war with the Soviets, there was little that could have been done.
The USSR never would have instigated nuclear conflict with the USA. They were pretty nihilistic, but never as nihilistic as the Mullahs prove to be now.
Washington warned us against cultivating a “reputation of weakness” in his Fifth Annual Message to Congress, and also said that “religion and morality are indispensable supports” to our society.