The other part is that online lefties like us are a minority. If Biden does move left he risks losing the election to the majority of Americans who support Israel unconditionally. So nobody’s going to end up happy and he loses the election anyway.
He’s from a generation that believes “the system works”, because its worked well for him/ them.
This is a great insight that people who keep saying “we just need to push him after the election” don’t seem to get. Yes, I’m sure that in the past writing letters to Congress might have done something more than waste paper. But the system is so broken now that people don’t believe them and see the only way to get a message across that this is unacceptable is to not vote.