The key word is "again". This was a nostalgia play, America was a big deal fifty years ago, therefore just wind back to fifty years ago and we're "Great Again".

This play seems insane because Time's Arrow points only one way, but it succeeded (in the sense that people supported it) because it's predicated on Facts Aren't True. It doesn't matter that Time's Arrow points future-ward, that's just a Fact not a Truth so we can just disagree.

Facts Aren't True can actually work for stuff where all you're doing is messing with people. Your Courts are just people and they can reject observable reality and substitute your own Truth with the Kavanaugh Stop, a week in jail becomes "brief" and your skin colour becomes "reasonable suspicion" for example. Your executives can pay themselves huge bonuses for imaginary success while concretely the company fails and eventually collapses. Stock markets can soar as the real economy they're "reflecting" buckles and fails.

"Facts Aren't True" is a stupid choice because unlike the people, Mother Nature doesn't give a shit about your Truth. So America won't actually become Great Again, but it is able to delude itself about this at a cost to its standing in the world and to its own future.