The biggest reason trump won in 2016 was, apart from Clinton’s unfavorables, his sense of humor. He could throw out zingers and also be surprisingly self deprecating.
His problem is that no one was in the mood for any humor in 2020 as he had royally fucked up covid and now in 2024 he’s obviously in mental decline. He’s still good for a quip once in a while but he’s not nearly as funny now as he used to be and way less funny than he thinks he is.
Biden, meanwhile, for better or worse is exactly the same now as he was four years ago. A little more soft spoken maybe but he hasn’t changed nearly as much as Trump has.