I lived in the USA in 2012 and 2016. I am not expert, but a couple of things struck me from being there that were not obvious to me before.
The Americans are electing a monarch rather than a Prime Minister.
Biden gives the impression of being a great manager and experienced politician. Trumps comes over as being a terrible and dangerous President.
...But Trump does come over as a President and Biden does not.
Trump comes from central casting as a bad medieval King, Biden would not be cast as a King at all. At best, a dying Monarch who has been manipulated by his far smarter ministers before the true king emerges.
The Democrats (and I have met professionals working for them) have some similarity to Sunak and his supporters.
I heard Sunak's "went without Sky" comments being defended as a question there was no suitable response to. When it was said he could have acknowledged the people who worked for his security and that he has learnt many others did not have that and he wants to improve their opportunities, the apologist said that was not answering the question. The person did not understand what the question was really about and thought people should look at numbers and exact facts.
I had a white young Clinton fan (a rare thing) in 2016 that Clinton is only unpopular for nonsense reasons, and I said to her that the reasons do not matter in when it is genuinely a popularity contest.
Biden could have stopped Trump in 2016 but let Clinton fail instead. I think 2020 was his redemption for that. In 2024, it will 2-1 to Trump if he does not step down.
The other sad truth is there assumption that everyone want to get away from thinking the President has to be an arrogant white man in his position from privilege and old fashioned hierarchies. A lot of people are really OK with all that and they would be furious at Kamala Harris who is brown, female and "only" in that position from being capable and hard working.