It is a cultural thing, handed down from generation to generation. They see conservative Christians as Nazi symps (goes back to WWII). Some older Jews seriously believe the conservative Christians want to put them into concentration camps. A not insignificant number believed that GW would do exactly that in 2000. Seriously. It dates back to some serious anti-Sematism back in the day. Modern reality, though, is trumping this perception (now a complete misperception - Jews and Israel have no better friend than true Christians and no worse enemies than islam-enabling leftscum). The irony is that traditional Jewish respect for family and tradition - in other words conservatism - has made this a long time in coming.
My family has been Christian for as far as I’ve been told yet does have a Jewish Dutch Grandma in the picture. Hitler partnered with the Persians and Arabs. It still goes on.