I'm not sure why you think it will go like that at all.
First, you're assuming that "good" triumphs and we don't end up in a timeline where historians tell how Trump and the great US patriots saved the country from the horrors of communism and fascism promoted by Democrats in the 2010s and 2020s.
Second, even assuming that occurs, I'm not sure why you think that these folks are going to agree with "reality" and "truth" and "history books". We still can't come to a widely-accepted consensus about the causes of the US Civil War and that was 160 years ago. Far, far too many folks still adhere to the Lost Cause mythology of the Civil War that the South was standing up for states' rights against the tyranny of the North and the Federal Government. (Of course, the Venn diagram between Lost Cause believers and MAGA likely has significant overlap.) It's far more likely that in deeply red parts of the US, the "common sense story" of MAGA will be that they were standing up against the tyranny of Dems and an overreaching Federal Government no matter what schools and history books may teach. It's more likely that even if Trumpism is defeated, that MAGA will continue to be proud of their beliefs and will tell an alternative story that places them on the right side of history but simply defeated by the forces of evil.
