Adding to Libby,
Hitler wanted to see the once great Germany rise and make the Allies pay for the great pain and suffering that they had brought on the German people, thus gained popularity for the Nazi Party until they assumed control.
Mussolini ordered his armies to deal arms to Germany under the League of Nations (United Nations at the time) noses making their armies grow and grow until they could self sustain.
Stalin wanted to help Hitler with the takeover of Europe until Operation Barbarossa where Germany turned on Russia and was less than 100 miles away from Moscow until the winter set in. Stalin then changed to the Allies and helped crumble Germany from the East while the U.S., UK, and Canada pushed from the West. (Stalin isn't remembered like Hitler only because he was on the winning side. While the Holocaust was horrible it killed 2-8 million Jews whereas Stalin had over 40-60 Million of his people executed or died of "unnatural" causes during "The Great Purge".)