2020 election happens in the middle of one of the weirdest black swan event of our lifetime (COVID). We literally thought this was the end of the world at first (march-april). The summer of 2020, Olympics are cancelled, early in the summer, nation wide riots for george floyd, whole world is pointing its finger at the USA. Trump was acting a fool (that part i agree is the same). Then for the rest of the year, a lot of the world was on a curfew. Then an attempted coup in January 2025.
2024, people are outside again, Ukraine war going on, Gaza genocide going on, all under the Biden admin (which she represents in the eyes of a lot of people), Biden looking worst than larry holmes status in the debate so people lost even more trust in mainstream media (which for the most part were heavy in kamala's corner besides fox). Trump surviving an assassination attempt which gained him a lot of clout in his base.
Yes Kamala and Biden had similar programs. But the difference is that in 2020 it was theory. In 2024 it was after 4 years of them applying their policies. People don't care about if he had congress in his pocket in order to do what he wanted. They don't care that part of the prosperity under Trump was thanks to Obama. They look at it like "how was my life from 2017 to 2020 vs how was my life from 2021 to 2024.". They view it as back then there was no war, Russia, Iran, China, North Korea wasn't bold enough to cross lines. Maybe they saw Biden was looking like a mark. And Kamala was part of it all but was invisible.
The most powerful VP in US history was probably dikk Cheney (you could argue he was the real president). Kamala was invisible. So therefore she was seen as having no real consequential experience. At best she was invisible, at worst she is partially responsible for Biden's perceived failures. Biden was seen as change in 2020. She was seen as the incumbent.
So yes, there were differences. Damn near different eras. Different circumstances. Yes, her being a woman is a factor. But it goes deeper than that. Put it to you this way. Say this election, the DNC runs someone else, and lose, then Trump fukks up for 4 years and we're in 2028 and she runs, then it would be more similar to 2020, because now people are thinking, things weren't that bad in 2023-2024. Trump fukked it all up. Let's try something new. I think she would have won then in my scenario.