Tin foil hat here: I think that Kamala was intended to be the 46th president, not Joe. But she’s so unpopular that there was no way she could be elected. Enter good ‘ol Uncle Joe, as a stand-in patsy for a few months. Look for him to have to resign for “health” reasons and to spend more time with his family.
Harris is only where she is because Biden had to pick a woman and an African-American, or somebody who could claim to be so. Biden is where he is because he isn’t Bernie Sanders and could beat Sanders. Very, very few people were enthusiastic about Harris.