There isn't some magic moment when all the MAGAs become liberals, but there is a moment when they wake up from their bender and refuse to admit that they ever were fans.
The extreme adulation of George Bush was similar, just noticed by fewer people because in the post-9/11 haze, especially, that extreme adulation was shared fully by the keepers of our glorious national discourse. We fret about the normalization of Donald Trump, but at least there's some public dispute about whether or not he is the Greatest President In History. Until about halfway through Bush's second term only online weirdos (I think they called them "bluggers") and maybe Paul Krugman suggested otherwise.
This is a bit of an exaggeration, but only a bit. Journalists didn't notice how insane Fox News was because the coverage wasn't really any different elsewhere. Matt Drudge ruled all of their worlds, and they proudly admitted it.
But the deification of Bush ended, and even though "we" forget that now, too, because he paints dogs and hands out candy, his approval rate went into the mid-20s. Though we barely noticed at the time, too, because the press was a bit behind the public and kept writing "comeback kid" stories when there was no evidence of a comeback.
My point is not that it is over, wrecked, done, for Trump. I have no idea. My point is that when he is done he will be forgotten quickly by his biggest fans.