People are so politically blinded that it's almost impossible to explain the plan, but to anyone with the strength to keep a level head, it's pretty clear what the plan was, and frankly it probably had a 50% success chance. But Trump rolled a critical failure on it.

Iranians were rioting against the regime, Israel intelligence handed the US a report that the collective "Head" of the Iranian regime will be all together at one place, at one time.

Cut off the head, and the rioters riding high on the win will topple the rest. Coming off of the swift clean victory in Venezuela, and Trumps incredible desire to put feathers in his cap, it was an irresistible proposition.

So he decided to cut off the head, which was successful. The miscalculation however was that the rioters got scared/apathetic rather than motivated. The power vacuum was filled by the same people who were there before. I'm sure Mossad and the CIA were probably on the ground trying to ground swell support, but evidently it didn't happen.

Has the cut off the head strategy ever worked in any US operation for replacing a leader with someone outside of their existing network?

The only people who ever would have taken any of this as a "Plan" are the moronic current admin.

Killing a few heads of Iran was known to not be an effective strategy, because the power is in the hands of the IRGC as an institution and large group, not the figureheads. This is especially hilarious when the Trump admin was so freaking stupid, they couldn't figure this out even after it didn't work the first time. They continued trying to kill random figureheads as if that plan would have had more success if you killed people nobody had previously heard of.

None of this is "miscalculation" or bad luck or taking a reasonable gamble. It's stupidity. There was not evidence to believe this plan had a strong chance. There was no organized resistance. Claims of supporting the Kurds, a group the Trump admin has fucked over more than once (nit: Other Kurds, they aren't a single group), happened only after the war was already going tits up and involved absurd tweets about "dropping them weapons" as if that's just a thing you can do on a whim and as if the Kurds themselves were willing, ready and able to resist the Iran regime.

We did not "Cut off the head" in Venezuela. We conspired with insiders to replace one figurehead with another. It was not a victory except for extremely weird people who think abducting a foreign head of state is somehow a good thing.

The Pentagon was actively telling the admin all of this, which is why some of them were fired.

What happened was even dumber than this absurd post-hoc rationalization: Israel was fucking pissed after Oct 7th, which is reasonable, and decided that "Mowing the grass" was done, and they were going to Finally fix this. They planned to attack Iran. Their strikes over the next year were done to enable this. Shortly before their planned attacks were to start, Bibi came to Trump and told him about this Righteous war they were about to do and got it in Trump's mind that it would be good for the US to look Strong if they attacked first, as Iran would probably attack US bases in retaliation anyway, and may end up pulled in regardless. IE, there's a chance Kamala would also have gotten sucked into this quagmire in some fashion, depending on how Iran had reacted to just Israel's strikes. Nobody was in a strong position to tell Israel "No, don't start this war, that's stupid, it's stupid, you've already neutered all the proxy groups, just take your victory and go home"

This is Israel's war. They don't mind the straight being screwed up. They don't mind the world economy falling down.