The candidate doesn't matter that much, and Kamala came closer than you gave her credit for. What matters is the current political temperature in the country and people's anxieties, how angry or excited they are. Kamala didn't make anyone excited to vote for her, but what really screwed her over was the Biden administration going hard-retard for four straight years. Mayorkas and Garland are probably more responsible than anyone for Kamala losing. Mayorkas went balls-to-the-wall for open borders, and Garland turned the DOJ into a partisan retribution operation. This made Republican voters furious and got them to turn out in large numbers for Trump. Oh, and the double-digit inflation driven by trillion-dollar deficits didn't help, either. If Biden's handlers had simply kept his administration low-key, we'd be looking at President Harris right now.