/ Why did Hitler kill so many Jews in Poland?
The original question was, Why did Hitler kill so many Jews in Poland? One reason is that there were a lot of Jews in Poland to begin with. But I also have a theory that because Poland was blessed with a rich network of railways, extending throughout eastern and western Europe, it only made sense to funnel them there from Europe and the Soviet Union. Poland is well situated in the middle. The transport system was already quite well established. Many trains filled with arms for the Eastern front traveled through Poland from Germany. Rather than bring them back empty they were filled with prisoners of war, Jews, Gypsies, etc. and dropped off at various camps along the way for imprisonment and annihilation.
We will never know the real answer, but this may explain one piece of the puzzle. I do not buy the theory that it is because Poles are anti-semitic. Polish people can be shrewd businessmen as well.