I suspect it because there were a lot of Jews in the early major league cities like NY , Detroit, Boston etc. After all, my great grandfather was apparently a Polish Jew who ended up working for the Purple gang who were a Jewish gang.
You have a very interesting family history Cripple, I know you have said that you only recently found the Jewish Roots in your Grandfathers past, but seeing that he was in the Purple Gang, he must have kept his Jewish Roots for sometime here in America.