So really the change between 2020 and 2024 is not a popularity increase for Trump, but a huge popularity loss for Biden/Harris.
Now the question is, how did Biden/Harris manage to be so unpopular, that 12 million people decided to rather risk Trump winning, than vote for them again?
Trump didnt gain or loose many voters.
Biden/Harris lost a lot of voters.
So really the change between 2020 and 2024 is not a popularity increase for Trump, but a huge popularity loss for Biden/Harris.
Now the question is, how did Biden/Harris manage to be so unpopular, that 12 million people decided to rather risk Trump winning, than vote for them again?