For what reasons did the Allied powers finally defeat Nazi Germany in Europe?

In my
opinion, the Allies defeated Germany by having more people to fight with and a much larger
industrial base to produce war materiel.  Very significantly, the Allies had the United States
to serve as a huge factory that could not be touched by the enemy the way German factories could
be bombed.

When you combine this industrial advantage with the fact that
Germany faced both the US and the Soviet Union (with huge populations -- I'm not discounting
Britain, but it's not a huge country) it is not at all surprising that the Allies won the
war.