Why is everything about beating "the other guy" with you MAGA people? You boil everything down to "our team" winning over "the other guys". It's like a massive rivalry built up inside your head and it has blinded you to critical thinking.
I have some Trump voters in my circle of friends. Not a lot, granted, but a few. There seem to be different types. Some voted for Trump as a protest vote. Some voted out of a hatred of Hillary and assumed the GOP would reign Trump's worst instincts in. And some are like you, that is consumed with beating "the other guy" Of the first 2 categories, without exception, they regret their vote. The last category they seem to be holding firm though I've seen some cracks in a few.
Only time will tell but if I were you I wouldn't hold onto 2020 being like 2016. Some of the recent routs the GOP have suffered at the ballot box seem to bear this out.