If Trump dies, Vance becomes president. If Vance dies, Mike Johnson becomes president. What do you know about those people that I don't that convinces you the hammer will come down once Trump is dead?
A USA where the economy is poor and the Gen X and older cohorts have returned to 2010 levels of apathy is one where Newsom, Walz, Kelly, Booker, Ocasio-Cortez etc openly directing anybody they have authority over to disregard all instructions of federal personnel up to indefinitely detaining federal personnel does not stop them from sweeping in 2028.
For example, before Trump, it was slowly becoming increasingly unacceptable to openly espouse racist and sexist beliefs in public and among your peers. Now, we have official government communications and executive orders including blood and soil rhetoric.
In contrast, Boris Johnson (ex-UK Prime Minister) deliberately made himself look like a blundering fool (messy hair, stumbling over words etc.) whilst being very smart. Unfortunately, he lied a lot and abused his power, so we eventually got rid of him - not the kind of person you want to have power, but the type of person who seeks power.
Do you think that Vance or Johnson really have the skill and charisma required to stay atop the twitching corpse of a horse that used to be the republican party and keep it moving?
Here's a general rule and a hint - (aspiring) dictators and authoritarians always fill the positions closest to them with people who are semi-competent, but not competent or ambitious enough to threaten their power. That's because the greatest threat to their power is from their allies, not their enemies.
If Republicans found a spine or some love for their country one day they could easily impeach and remove Trump - there's no doubt the Democrats would vote for it. And, if Republicans ever do the math and decide that Trump is more of a weight than a boost, they will do exactly that.
This dynamic is why we've got Pete Hegseth running the military instead of someone... sober.