They had two really lucky blows. They shouldn’t have gotten lucky with the Battle of France or Operation Barbarossa, yet both were successes against all odds - not because of any exceptional fighting skill of the German military, but because France was in total military and political disarray (completely disregarding reports of a German attack through the Ardennes, and then appointing Petain to ultimate power, who just fucking surrendered), and the Soviets were led by a moron of equal magnitude who thought he had another two years to prepare and was thus caught with his pants down.

Luck is an aspect of war, of course - but hardly one that impresses.