Or, and I know it's going to sound like a conspiracy theory, Trump picked JD because JD is so weird, and he knew that JD would tank. So when Trump drops JD it'll give him a boost, like the one the democrats got when Biden dropped out. Trump has repeatedly kept lowering people's expectations, to the point that if he somehow managed to put the round peg in the round hole, it would be a success. So imagine the boost Trump would get, for making the obvious decision to drop JD.
But that plan requires that Trump is able to play the long game, and stay quiet about it. Two things we know isn't plausible.