I think it's less that staunch anti-racists are reading a shitty lib take and going 'oh yeah I hate jews now' and more that kinda switched-off centrist-y types who don't really have an opinion are skimming a bunch of headlines like 'here's why anti-racist campaigners are cancelling Israel, by Trust Fund Baby #17' and over time it builds up a negative association that they're not even fully aware of. And that then makes them vulnerable to anti-semitic propaganda.