How is it that so many Jews ended up in the forests of central Europe?

What is the history of this? How did the apparent majority of Jews end up in the ancient forests of central Euroupe (which Germany is) why were so many Jewish people so far from their promised land before world war 2 (and pre-medieval)? Then all of a sudden after the war they insisted that was their home.

I understand asking such questions carries the risk of being classed ‘anti semite’ but I really want to know , why didn’t the Jews try to claim ‘home’ before ww2?