The world would be a better place today if he had annihilated the entire city of Tehran, inadvertently/regrettably killing everyone in the US Embassy in the process, and telling the family of the American hostages, "I'm sorry, it couldn't be helped."
Instead he showed the Islamo-Fascists that the American government could be cowed by putting a few of its citizens on TV and threatening to pull out their toenails.
And OBTW, one major factor allowing the Iranian "students" to blindside the American Intel community was Carter's Executive Order 12036, which gutted the Humane Intelligence (HUMINT) community. Because Carter, like Secretary of State Henry Stimson, believed spying was a base and uncivilized act ("Gentlemen don't read each other's mail" -- Stimson). Carter believed more modern collection methods (esp. overhead surveillance) eliminated the need for HUMINT.
Unfortunately for America, the Iranian "students" were keen to show Carter the error of his ways.
And OBTW, much of Carter's EO 12036, including the throttling of HUMINT, was rescinded by Boss Ray-Gun's famous EO twelve triple-three.
Actually it starts even earlier in the Nixon administration. As part of currrying favor with the Shah it was agreed that HUMINT gathered in Iran would come from SAVAK. Of course all the US got was a “rosy things are wonderful” picture. Carter’s idiotic INTEL notions just made things worse.
Also our “footprint” of US contractors, US government civilians, US military, etc was way too large in Iran. We became “irritating”.(I forget the numbers.) We’ve had the same problem in SA. So far it hasn’t led to the same “explosion”. Maybe we learned and have handled it better, maybe we’ve been lucky, maybe SA has been smarter.