The Obama bros on Pod Save America are fascinating at the moment because they still won't admit the party got anything wrong - to listen to them, they had a great campaign, a great candidate, popular policies, and it's still a mystery to them why they lost.
A great account will be written soon enough about how the Democrats fucked up. I'm watching Amie Parnes, who was getting lots of leaks from the Harris campaign. She co-wrote that brilliant book "Shattered", all about the Hillary campaign.
It's interesting because the authors were embedded reporters with the campaign, obviously wanted her to win, but ended up recording how massively dysfunctional it all was. Trump barely appears in the book except as an offstage villain. There are regular moments where Bill Clinton wanders in, asks a smart question or gives sensible advice, and everyone ignores him.
A contact who follows these things says you could tell Hillary would lose because of the people around her. Bill Clinton had James Carville, Bush had Karl Rove, Obama had David Axelrod - love them or hate them, they're very clever and skilled political streetfighters. Trump has a few people like that. Hillary had a bunch of Brooklyn soyboys who thought they were the masters of the universe.
I don't know who Harris had.