Ah, yes, that very complicated anti-Semitism of eastern Europe.
Sentiments which I encountered many times up close and first hand, and sentiments with which I vehemently disagree, but really, it's very complicated.
And as for Jews in socialist movements and governments, one has to remember that these people were only of Jewish derivation, no more than that. They weren't in such movements and governments because they were Jews; they were in such movements and governments, because as with any other group of humanity, they were narrow-minded assholes and bigots.
Their Judaism had nothing to do with it; in fact, practically all of them had rejected the Faith of their Fathers.