Trump didn't always have this kind of power; he acquired it. Why do you think it's impossible for another person - especially one that is effectively "officially anointed" as successor by Trump himself - to step into his shoes?
Right now this is impossible because Trump sucks all the air out of the room. But with him gone, I don't see any reason why all those people who voted for him will suddenly not vote for the closest similar candidate, and that voting block is really where his power comes from.
And looking at history, cults of personality often survive replacement of the figure around which they are built - examples are numerous in various dictatorships, just look at North Korea for one that is still ongoing.
Trump was given the power by some invisible forces who have been working for decades to develop plans to destroy the US.
Trump is simultaneously a blunt force tool to destroy our institutions while also being a political wizard that always know exactly how to spin things and is completely impervious to pressure and stress.
I think those background forces know after trump there will not be anyone like him. Which is exactly why everything is being destroyed at such a rapid pace. Their opportunity is short and they are maximizing it. Things will look very different post trump
As an outsider European, Trump certainly has an unusual charisma. I happened to watch some of his tariff press conference while flicking over TV channels, and I get why people are attracted to his public persona. He has this strange hypnotic tone that delivers absolute nonsense in a reassuring way, and goes a bit shouty every now and then when attacking something. For people that actually believe what he says he must really have them hooked.
Along with the other points you made, rarely showing stress, always having a comeback with no care for the truth make him unique.
Vance is not even close.
It's of course that a future demagogue will rise to power. But it'd be a wholly different movement from maga.
When Trump goes all the smaller factions will compete for the top. That's the typical state.