Republicans support a weak central authority (Federal Gov) and Jews have nothing against American Nationalism so that’s not the answer.
That are many reasons for may results but the bottom line of how Jews vote would come down to two issues- in my opinion- location, location, location, and personality, personality, personality (of the candidates).
I could go down through every single Presidential race post war and explain to you very legitimately why Jews voted the way they did and in every instance the person’s perceived friendship, or not, to Jews/Israel is a reliable indicator. Not to say Jews were not (very) wrong in some of those perceptions.
The simple truth is that except for Reagan there has never been a Republican candidate that had a history of friendship to Jews and some had a quite hostile history.
There was no change between pre war and post war voting among Jews.