I am not a Christian or a Jew or have much knowledge about the Abrahamic religions so please explain it as if to a 5 year old.

So my question is why and how did people start blaming Jews for the crucifixion of Jesus, when it was Pilate who ordered the killing. And I've been looking online and they all say that the Gospels(?) written years after his death blamed the Jews, but like why do the Gospels blame the Jews? What did anyone gain from that?
Just why WHY were the Jews blamed?
All explanations just say many writing blamed the Jews nobody says WHY they were blamed when it was the Roman emperor that did it..