It seems that this anti-semitism began abruptly with England expelling Jews in 1290 and other countries taking similar steps in the following years. Was it that sudden? If so, why, and if not what preceded it?
Anti-semitism definitely wasn't a new thing in 1290. While the first major spike in anti-semitism was around the time of the the First Crusade (1096 CE) - entire Jewish communities in England, France and Germany were wiped out by crusaders and mob armies - anti-semitism was a regular part of Christian liturgy since at least the 4th century.
This mainly stems from the idea of the Jewish deicide: the belief that the Jews bore responsibility for the murder of Jesus. While officially not part of Catholic doctrine, from at least 167 CE (when Melito of Sardis wrote a homily blaming the Jews for Jesus' death) to 1965 (when the Second Vatican Council repudiated the idea) it was the traditional belief that the Jews killed God and should be punished for it.