Its psychological.
1. For some Jews, they convince themselves that maybe the Jew-haters have a point. (Bibi is bad, Israel could do better, its those extreme right wingers, proprtionality, etc). These Jews feel that by publicly denouncing Israel, or at least by associating themselves with Dems, they will be perceived as being more American and less Israeli. They feel safer more secure in America this way.
2. For other Jews, the thought that a major American party is antisemitic is just too much to bear, so they are in denial, and convince themselves that all the Jew-hatred is just a small minority and a blip and that the right wingers are worse.
3. For other Jews, their hatred of Donald Trump is so great that they’ll vote instead even for Hitler, as long as it isn’t Trump.
I think we can all sympathize with the first group, although they are wrong in thinking that they will be safer if they publicly align themselves with the Dems.
The second group is in denial and needs emotional help.
The third group suffers from TDS. They are beyond hope. They are psychotic. (They also think a man can give birth)