I think democrats are really downplaying Biden because it’s obvious that he’s become a liability. Practically anyone else would have been acceptable. Trump has somewhat been vindicated by the Biden debacle.
As far as people caring. Most people plod along in their workaday lives. They have jobs and take care of their kids. They get summaries of news. They don’t follow this in depth like retired people or college students can. So, it’s easy to manipulate people.