Yeah I think it's pretty much impossible to deny he's losing it anymore.
Yeah, I doubt very many people at all actually felt great about having to vote for Biden. He won because a Turd Sandwich was preferable to a Giant Douche. I'd do it again in 2024 though, if it's Trump vs Biden (but please god, grant the DNC the tiny smidgen of wisdom it takes to realize they shouldn't do that). Biden is a senile old man who they prop up in front of the camera so the establishment can continue their shit, but Trump is a cancerous tumor who used the existing divisions in this country to feed his narcissism, and who will do so again if given the opportunity, and I fear the result of 4 more years of his presidency. Look at what the first 4 have done to the republican party. He created the blueprint for how to undermine the democratic process. He has already left a rot in his wake that it may be too late to dig out.
I think you might be misjudging just how unpopular Trump really was, and how many people looked on with horror at what his presidency wrought. His supporters are extremely loud and extremely devoted, to a fanatical, worshipper sort of level (like literally Evangelicals claiming he was chosen by god), but most people were way too horrified by his 4 years to be able to vote for him, regardless of who the alternative was. Even if it was Biden. He didn't gain any new supporters, you can't think he could have, and Hillary didn't lose by a wide margin. He most assuredly lost supporters, who voted for him the first time because he represented a departure from the status quo, and most people want that, and some of them, who likely would have voted for Bernie, voted for him hoping he would be the change we need. And then saw that they were conned, and regretted their decision, and realized that the status quo was better than another 4 years of Trump.
And yeah, it did look like Trump was gonna win in 2020, but all of his supporters voted in person, or pretty much, while a great many, due to covid fear, who voted against him (tremendously more than ever before, but for a reason, because of pandemic fears), voted by mail. It's not hard to explain.