My guess would be that the enemies of ancient Jacob, namely the descendants of Esau, were forcibly made to "become" Jews because to the Romans it was all the same family, which it actually is, but one brother obeys God, the other does not.
What does that mean? It means that within modern Judaism, there are descendants of both Jacob and Esau. They have been mortal enemies for a long, long time.
Now, if you hate actual descendants of Jacob, and you know you are of the family of Esau instead of Jacob, you are in an interesting place. You are "within" Judaism so to speak. From outward appearances you are a Jew, just like the Romans, people only see the similarities, not the differences.
I suggest that many, if not most, of the corrupt "Jews" are actually Edomites pretending to be Jews.