I don't agree with Gori's argument that "Trumpism is forever, even without Trump". Ideologies can last forever, albeit with varying levels of popularity.
Trumpism, however, is about a cult of personality, and those tend to die out after their founder exits the public view. Sometimes, if it's a dictatorship, their successor can remain in power. North Korea being a good example of a sustained cult of personality. But Stalinism did not continue after Stalin, even though he passed away peacefully and the Soviet Union continued to exist; quite soon it was in a period of de-Stalinization.
The "unfocused" aspect is a lot of what will end it. North Korea works because it's a family dictatorship and they've always been laser-focused on the Kim cult. Without Trump, his particular brand of politics will fade. He was able to tap into a particular part of the national psyche in a way that was enabled because of his personality. He has a certain charisma on being able to harp on why a large portion of the populace felt aggrieved in a way that can't easily be emulated. People connected emotionally, felt this was the man who could change things. It wasn't Ted Cruz's conservative bona fides that won the day, it wasn't Marco Rubio or John Kasich's policy arguments. It wasn't really Trump's often vague policy proposals. It was his ability to channel their motions and give them hope that things might really change, that he really could Make America Great Again.
Of course a large portion of the populace found him repulsive, and another large segment wasn't particularly enamored with him but figured he wouldn't be such a loose cannon once he was in office and would advance their political priorities. Many of those who found him repulsive also didn't expect he'd remain quite so much of a loose cannon in the then-unlikely event that he entered office.
Biden was the one who was able to finally unite enough of the populace against him to remove him from office, and while the final nail hasn't been delivered to Trump's political coffin yet, I see no reason not to continue to bet on the winning horse.
Would Sanders, Warren, or Buttigieg have defeated Trump had they won the primaries? We'll never know for sure. Would someone else defeat him in 2024? Maybe, maybe not. But Biden has a proven track record, and I would argue has done a pretty good job as President, too, even with having been dealt a pretty tough hand, notably the continuing effects of the pandemic, the challenge of inflation, and the war in Ukraine.
One could argue that he's even turned those tough cards into an advantage as it's given him a stage on which to live up to the moment or not, and so far I think it's hard to argue he hasn't succeeded. The U.S. emerged from the pandemic relatively quickly, inflation has been more moderate than in many countries and has been decreasing while the economy has continued to grow, and Biden has played a central role in rallying democracies and NATO behind Ukraine. The latter one in particular is one where it's very difficult to imagine the U.S. succeeding if Trump were still president. Add to that being able to pass both the Bipartisan Infrastructure Bill (a policy Trump campaigned on but never delivered on, nor really attempted to deliver on) and the Inflation Reduction Act, and he has some significant legislative wins as well.
Is he old? Well, yeah. He's said so himself, at least when he was in Ireland a couple months ago. Would it be preferable if he were 10 years younger? Sure. But I am not so pessimistic as Kyriakos about the potential for octogenarians to remain healthy. Obviously not all are. But Queen Elizabeth II was widely said to be perfectly mentally sharp for her entire reign, and she was much older than Biden is now or will be in 2028. As far as I know, Pope Francis is another example of a leader who's considerably older than Biden but mentally sharp. I could go on, but the point is that it's a case-by-case situation.
And worst case, I expect Biden to continue to have a reasonable VP candidate, likely Harris. But not a Sarah Palin. Admittedly that was a concern in 2008, McCain was a good candidate, but the drop-off was so steep if he had run into a health issue. 90% chance things are fine and McCain serves 4-8 years, 10% chance of disaster. Harris has largely stayed out of the public spotlight as VP and I don't know that she'd be as good as Biden as Prez, notably on foreign policy where Biden has been able to flex his decades of experience, but with Biden we're talking 80% chance that things are fine and 20% chance that things are slightly worse. I can live with those odds. And if Trump does win the primaries again, I'd vote for a yellow dog before I voted for Trump.