The people that care most about this were never going to vote in general.

Not necessarily. People aged 18-24 had a voter turnout of about 48% the last election.

And with a significant majority of the population supporting Israel, there’s not really any option for candidates against it either.

The population includes republicans who aren’t gonna vote for Biden anyway. According to the Guardian:

Gallup has been tracking the gradual downward shift in sympathy toward Israel among Democrats that started in about 2014. In February, for the first time, Democrats’ sympathies for the Palestinians were higher than for the Israelis, 49% to 38%.