I've wondered about this many times. Not being Jewish, I cannot answer but only guess.
As Conservatives we expect a logical answer, but logic does not apply here.
My guess is it is a cultural trait that goes back to tribal times and is passed down generation to generation.
Actually, it goes back to the 1930s in America. And in Europe before that, to the early 19th century (specifically Napoleon, whom Jews supported because he legally emancipated them). Prior to the 1930s in America, most Jews were Republicans (just check the party affiliation of Jews who won office before the New Deal). After the New Deal, Jews (especially in the Northeast) began supporting the Democrat's vision of soft left ideology, and strong foreign policy abroad. And it became a cultural thing after that. The Jewish community has a strong cohesive factor that a lot of people often ignore.
Since Reagan, however, the Orthodox and Modern Orthodox, and lot of Conservatives and also young Jews have been moving towards the Republican party and generally to the right. For reasons that aren't exactly clear to the rest of the more soft-left parts of the community, but would certainly be understood and appreciated by FReepers. ;)
So, we're not smart enough to think on our own...you saying it's GENETIC???? ROFLMAO!!!!