I can't speak to the historicity of this but I read a hypothesis that the Romans deflected blame onto the Jews when they established Christianity as their state religion, which if true would make it one of the foundational moments in European antisemitism

Certainly sounds more true than not (though I'm aware that doesn't necessarily make it so). Latin (western, Catholic/Protestant) Christianity basically took a grassroots, pacifistic, anti-materialistic (and anti-wealth in general) religion and turned it into a crusading, genociding, hyper-intolerant and hyper-imperialist nightmare.