Antisemitism is millennia old. The haters and the pretexts vary so wildly through the centuries that the only "reasons" that seem real are that they exist, persist, and are different (as mandated by their law, in the degree that they can follow it).
Current antisemitism is rooted in Israel - either Muslims, who feel Israel should not exist and Jews slaughtered/enslaved, or Lib/Prog westerners who feel it is outrageously unfair that Israel won wars over their Arab enemies (I remember hearing of this resentment/hatred after the Six Day War in 1967) and continues to defend itself.
I'm convinced that, were the ME situation magically and amicably brought to peace, a new pretext for antisemitism would spring up.