What makes "assimilated"* Jews turn against their own people?

It is my position that anybody is free to re-shape their own identity in the best way that makes them happy. This does not diminish my interest in understanding by what process or under what compulsion, a Jewish person would prefer to attach themselves to a majority that reviles Jews, for one reason or another, imaginary, malevolent or virtuous. In this I find Hannah Arendt's  analysis very persuasive, as displayed in this excerpt:

"In the minds of the privileged Jews such measures taken by the state appeared to be the workings of a sort of heavenly tribunal, by whom the virtuous - who had more than a certain income - were rewarded with human rights, and the unworthy - living in mass concentration in the eastern provinces - were punished as pariahs. Since that time it has become a mark of assimilated Jews to be unable to distinguish between friend and enemy, between compliment and insult, and to feel flattered when an antisemite assures them that he does not mean them, that they, are exceptions - exceptional Jews. The events of recent years have proved that the "excepted Jew" is more the Jew than the exception; no Jew feels quite happy any more about being assured that he is an exception. "

(Privileged Jews Author(s): Hannah Arendt Source: Jewish Social Studies, Vol. 8, No. 1 (Jan., 1946)

___

*"assimilated" is the term used by Arendt. I would not use this term.