Being Kamala put Kamala in a tough spot. She just wasn't that good, she was frankly kinda meh. She exuded a feeling of "I'm a good mid level manager", and never managed to convince us she could move past that.
Every time she opened her mouth to make a point, nonsense came out. She just exuded "incapable". Trump did too, but never pretended otherwise.
She'd been pummeled in the primaries, and got a political version of "get out of jail free" card being put on the ticket as a token for Biden, and then when Biden dropped out it was a lot of "wait, whaaaa?' I can't help but think the only reason the democrats ran her was that they would have had to give back all that donated money had they changed the candidate.