Honest question: Does anybody really think Corbyn's supposed antisemitism cost Labour a meaningful number of votes? Do working-class people in leave areas actually care about Corbyn's position on BDS or Israeli settlements? I personally doubt it but the media has been mentioning this issue non-stop as a factor.
Jews make up about 1% of the population, and 94% voted against Corbyn (pre-election polling), so it probably cost one or two London marginals, like Finchley (which would have been a lot closer without the Jewish vote)