People didn't vote against Biden/Harris, they voted against incumbents in almost every major election across the world. They were unhappy with the economic situation after Covid – Biden just happened to be president at the time.
https://www.noahpinion.blog/p/americans-hate-inflation-more-...
Not just that but they voted significantly more against the incumbent in the rest of the world than the US.
People really did not like Trump they just didn't like incumbents more.
It's almost like if the Democrats ran a competitive primary this whole situation could've been avoided.