Well they might be antisemitic but they hate Arabs too, and with a much less complicated, pure and dehumanizing hatred. At least Jewish people can be mistaken for white.
Plus, if you hate Jews, don’t you want them to have their own country to fuck off to? And if they destabilize and oppress the Arab world in the process? Win-win.
Jewish interests are also just better mobilized in the US. They have a good story as our best ally in a fucked region, and they’ve succeeded in telling that story. As far back as Abraham Lincoln there has also been compassion for the Jewish people and a desire to see them in a secure homeland. But at this point that seems to be a distant third or fourth in terms of motivations to support Israel.