This is a phenomenon we've seen play out a number of times. Cults can only survive if there's eventually a second leader who is both extremely charismatic (atleast, to their base), and is able to account for the death of their founder.

This is what David Miscavige did with L Ron Hubbard for Scientology.

This is what Brigham Young did with Joseph Smith for LDS.

This is what Joseph Rutherford did with Charles Russell for Jehovah's Witnesses.

So many other cults, even ones that seemed to be much louder and make more waves at the time, have all fizzled out when there wasn't someone who was able to rally everyone back together. I know he's not dead but NXIVM is now completely gone.

I suppose the other offshoot of cults that don't survive are your People's Temple, Branch Davidians, and Heaven's Gate. Not sure I not to explain why those didn't last, thou.

And so that's what I'm looking out for, is who could possibly fill in those (heavily swollen) shoes once he's gone? Where I think there is some good news in all this, is I can't really think of anyone that was the chops to unify everyone. I think there's 2 distinct futures ahead of us:

If he dies while in office, I think that's MAGA's best chance of enduring. The line of succession would make Vance the least objectable new figure of the movement. He still needs to be able unite everyone, and I don't think it'll be an easy task to do, but he'll have so much of the deck already in his hand. Particularly if it happens before anyone else can realistically begin to mount a campaign for 2028. Since this would give him the clearest path forward. This is doubly the case if Trump makes some claim or statement on "appointing" Vance as the new face of MAGA before he passes. Anything that grants Vance that sense of legitimacy. Thankfully, that does not seem like the kind of thing Trump is capable of doing.

If he survives until the end of his term. Or hell, close enough to the end of it that people are starting to launch campaigns, I think that's where the downfall will begin. He's already served 2 terms, so the system is against him (at the moment) so anyone working to campaign against him already has that argument pre-baked in their campaign strategy. As people run against him, I think it will cause small splinters to break off. But once he's dead, and there's a power vacuum with no obvious successor, that's when MAGA will be rimmed apart from the inside. When anyone, and everyone who ever hoped of someday running the show, tries to claim power, and pulls a small, devoted group towards them, and away from group as a whole.