The more I think about it, the more I think maybe the question should be, "what didn't the Democrats do wrong?" In hindsight, it seems like the Democrats fractally bungled the entire thing. They somehow bungled the economy pitch. They somehow bungled the social issues pitch. They somehow lost ground with pretty much every minority voting demographic. They lost the popular vote. They lost the Senate. They lost the House. They kept Biden around too long. They got rid of Biden too late in the game.
They replaced Biden with perhaps the worst possible candidate in this cycle. They had no other choice because they somehow bungled the entire strategic plan for the post-Biden era. I wouldn't be surprised if they lost votes over both Ukraine and Israel. Is there anything the Democrats did right? Is "right" even valid attribute, for a losing campaign? They won Oregon. Does that count?