Over time -- and this is leaving out nearly all the important structural factors and non-US players in the process -- I've come to the conclusion that the four Americans *most* at fault in the US side of handling the hostage crisis are these:
1) Henry Kissinger Is there a foreign-policy disaster of the late 20th century that cannot, in some way, be traced to Henry making bad choices? He's the single most overrated Cabinet official in possibly ever. In this case there are three and you're not expecting the second one. First, he, together with Nixon and ex-CIA boss Richard Helms (who became ambassador to Iran) were the three US officials most responsible for the geometric escalation in America's relationship with Iran, whose massive inflection really occurred between 1972 and 1977. The massive escalation of aid money, foreign military sales, ramping up of government and civilian contractors operating in Iran to support that gravy train (Ross Perot and EDS were, in some ways, relatively small fish in the pond though they had some very important tasks), and increasing strategic dependence on Iran, even more than on the Saudis, for Gulf/oil-states stability, came in that period. If you check Foreign Relations of the United States' Nixon/Ford-series volume Oil Crisis 1974-80 Kissinger even intimates the idea of developing a plan for Iran to threaten invasion of Saudi Arabia and possibly Qatar in order to intimidate the Saudis back into line. That's how deep it went.
Second, and this is perhaps the surprise, is Henry's nearly unhinged, our-national-wang-is-shrinking response to the Mayaguez crisis. No one in Ford's administration (Ford, also an old Navy man who had some fits of good sense during the crisis that were steamrolled by Kissinger's wild-eyed urgency to kick someone's ass somewhere) had such a hard-on for charging in as he did. So the US went in blind to Koh Tang, with not much intel and none of it disseminated to the assault force (on that front RICEBOWL actually did a better job) and walked into an ambush. As a direct consequence the 21st Special Operations Squadron and its special-operations-configured CH-53s were shot to pieces, and the rump remainder of the squadron was transferred to become glorified cargo carriers in West Germany. Had they not been sent on that mission (the Marine Corps' official history of the end of Vietnam, which has Mayaguez as its last chapter, is particularly scathing about the official decision-making), the ten intact airframes the morning of that fateful day would probably have been sent to Hurlburt Field and joined the rump of the 1st Special Operations Wing. Four and a half years later, those CH-53s would have looked and quacked from the outside (not the inside) like the Marine models and not looked out of place on a carrier. They would've had huge advantages in maintenance standards and aircrew skills that might have made a material difference in RICEBOWL's outcome.
The third thing, of course, was taking in the Shah. For that there was no bigger cheerleader than Kissinger: we had huge levels of secrets (esp spying on Soviet signals infrastructure and missile tests from Iran), personnel, and sunk costs invested in Iran. That last, sunk costs, led to the other biggest cheerleader, Henry's old buddy David Rockefeller, whose Chase Manhattan bank had about $5 billion tied up one way or another in the Shah and wanted him safe and sound to help guarantee return on those funds. When he finally relented on his opposition to accepting the Shah, Carter bluntly told his cabinet they were all going to look very foolish when someone took over the Tehran embassy and demanded the Shah's return. He was entirely right.
2) Charlie Beckwith The foundation of Delta resembles in one analogous way another trailblazing 1970s phenomenon, Star Wars. Both were gifted ideas right for the moment, and both had as their Achilles heel the ideas guy who came up with them in the first place (also, neither was as unique as their retrospective origin stories made out but that's another post in another thread.) But despite the outstanding work by people like Dick Meadows (as a civilian contractor), Lewis "Bucky" Burruss, Pete Schoomaker (eventually Chief of Staff of the Army) and some of the senior NCOs, Delta in its early days never quite had a Larry Kasdan or Gilbert Taylor (or Marcia Lucas) to mitigate and work around the worst ideas and decisions of the original creator. That came, but after RICEBOWL not before. Indeed at the beginning Delta might have stayed in the Special Forces infrastructure and become exactly what Beckwith said he wanted -- an "American SAS" -- as Special Forces' direct-action component, doing not only BLUE LIGHT counterterrorism but also GREEN LIGHT "atomic demolitions" in a big war and some of what the shadier Intelligence Support Activity did later on. But he was so damned determined to show off his own genius and have "his own horses" that he did not -- also having an incendiary temper and only playing well with those who knew how to manage it didn't help. The result was a "Charlie's Private Army" that had two fatal flaws come RICEBOWL. The first was that in itself -- he and his new command reported directly to the National Command Authority without any of the crucial logistical supports embedded (although he grudgingly learned to work with Air Force special ops) that it would need to operate anywhere in hostile territory. The other followed from that: his original Mogadishu-defined (an op on friendly turf done by a gendarmerie equivalent of the FBI's Hostage Rescue Team) model for conducting CT/hostage rescue operations was *not about operating in hostile territory*. The earlier, jerry-rigged system under REDCOM that trained up the Rangers and a BLUE LIGHT element (code for the mission set not a unit, though the provisional unit adopted it) was all about operating in hostile territory. Beckwith largely ignored that component in the early going, particularly with regard to hostage rescue itself. This was a disastrous misapprehension. It also meant that his tiny, exquisitely selected and trained, original Delta force was simply too valuable to lose once RICEBOWL started going wrong in the field.
3) Zbigniew Brzezhinski We've been over some of this in my previous comment. But Zbig had a genuine, chess-game strategic vision and he was as single minded about it as a Pole trying to screw over the Russians could possibly be. He would bleed Moscow white and then, as he had written presciently in books as an academic, the nationalism still under the surface of the Eastern Bloc would reassert itself and shatter the Soviet strategic domain. Nothing, not the fifty-three Americans (sixty-six at the start) stuck in Tehran, nor in the end his boss's presidency, was so singularly important to him as that larger cause. It's like a real-life American version of Le Carre, with many of the same human costs in pursuit of a "higher" goal.
4) David Jones Carter's Chairman of the Joint Chiefs of Staff was a bureaucrat's bureaucrat. In a very different cause -- the stability and good name of institutions vital to nuclear deterrence and the Cold War -- he had the same kind of single-mindedness as Brzezhinski. His relentless concentration on operational secrecy, which did not in the end keep down the size of JTF 1-79 or its operational components which ballooned up past 1000 people, cut the planning task force off from a variety of people and sources who could have materially contributed to the mission. His zero-defect approach, which ended up with the byzantine entry and exit plans, avoided taking one or two huge risks (like with Entebbe or the Bin Laden raid) in favor of dozens of small ones which ended up increasing the likelihood of the outcome that actually happened. He was also determined to avoid any entangling complexities like operating from other countries rather than off a carrier already devoted to other aspects of the mission (and not given, say, to looking after maintenance on some minesweeping helicopters that were taking up space): in the end the US was able perfectly well to operate from Oman's Masirah Island and if that had been part of the process from November rather than March an entirely different entry plan might have developed. Likewise if he'd been willing to piss off the Turks and his own native service (Air Force) bureaucracy by using the "white hat" refuelable Airborne Rescue & Recovery Service HH-53s to, say, fly out of RAF Akrotiri on Cyprus ... there are a whole range of more creative and potentially effective plans (including a parachute-launched raid with ARRS recovery -- again take one or two big risks but keep it simple) that Jones massacred out of hand in the early November planning process. His goal was to avoid public disaster and it's exactly what he helped ensure. The ancient Greeks would nod knowingly.
* I should clarify: by "Mogadishu" I don't mean the whole "Black Hawk Down" business. I mean the 1977 rescue of a Lufthansa jet (one of the first to get all hostages out alive) by GSG-9, led by one of the true pioneers of offensive counterterrorism and the very model of an *actually* good German, Ulrich Wegener.