The answer is simple, but also out of our power: they have to "touch the stove", as people like to say colloquially these days. Trump needs to cause real damage that affects their lives directly & makes them regret supporting him. If he flames out and becomes a very unpopular President, it will discredit him and his supporters.

Once Trump is gone, I think there is a real opportunity for the sane adults to grab the wheel back. Trump is very much so an emotional cult & those are very difficult to replace. It's quite likely that many of the Trump cult voters simply won't turn out anymore (they already don't during midterms).