My armchair political analysis (NB, I’m just some pseudorandom redhead, grain of salt):
If Biden follows through with this, then AIPAC will become hell-bent on electing Trump. They have to. Never mind that Trump is a hideous antisemite; that’s not the point. The point is that AIPAC wants every US politician to believe that anything less than blind, unconditional support for Israel is political suicide. If they don’t try to destroy Biden over this, or try and fail, they become a paper tiger.