None of it is philosemitism or antisemitism, jews aren't a race, and they are certainly not the entirety of semites. No one saying hatred for Bashar Al-Assad is anti-semitism.

Jew-Hatred is really the core here. It isn't used to 'reel in disillusioned leftoids'. Fundamentally, jew-hatred is a core component of Leftism itself, and the harder you assert Leftism, the more inevitable your hatred of jews becomes because Capitalism is literally nothing more than a dog-whistle against what Marx asserted was the inherent nature of jews. It's why he believed that it was impossible for jews to exist within a Socialist society, and they would disappear as assuredly as the state would.

The only reason jew-hatred isn't the norm on the Left is because jewish intellectuals who were already Leftists wanted to try and carve out jews from the Marxist narrative. They wanted to secularize it more, and they saw Zionism as an explicit form of Progressive Nationalism. After the Holocaust, they kept trying to repeat that there wasn't anything within Socialism that supported jew-hatred, and that somehow jew-hatred was "rightist/conservative/reactionary. This effectively amounts to the earliest form of Holocaust Denial.

Where everything started to go wrong was when despite the Zionist movement have succeeded in foemen ting the state of Israel, instead of allying with the Soviet Union, and becoming a full Socialist state, the Orthodox jews that the Zionists had allied with rejected atheistic Socialism and allied themselves with the US. The Socialists and Communists never forgave them, and as the Left has moved slowly away from "racialist policies are exclusively right-wing" we see the inevitable re-emergence of jew-hatred among the Left, which was always the previous norm.