If they were white, wealthy and protestant then they were most likely republican. They were community leaders and influential people who got laws passed that enforced discimination in housing and business. Jews perceived that these were the people that didn't let them buy houses in nice neighborhoods, join country clubs, participate in the political process, etc. so they sided with democrats who wanted civil rights.
Joining democrats may have been the lesser of two evils; Jews felt discrimination was pretty universal.
You may disagree - I'm just explaining why most of my older relatives vote democrat.