It took a combination of UK, USA, France and Russia etc. to defeat only one nation. Italy and Japan were not much of a man. They were so powerful because of their omnipotent genes?
I would guess that Germany was so powerful, since they were fighting nations that got disenchanted with war after a thousand years of war in Europe. Especially, after The Great War (WWI). Germany didn't get disenchanted with war, since the Nazis were able to play on the emotions of Germans that Germany was humiliated by losing WWI.
Anyway, if one looks at someone that appears "superior," it might be that that person is really "average," and is only competing against people that are "inferior." One doesn't have to be superior to win over inferior people; one can be just average. Naturally, to save face, the inferior people accuse the average person, oftentimes, of thinking that he or she is superior, when in fact that person is just average, and just won over inferior people. A hard fact for many to swallow.
But, Germans might have some superior qualities in its culture, since they did make a better recovery after WWII, than many other countries. And, if one wants to get into that whole Aryan schtick, the blondness of Germans came from Sweden, when back in an earlier century Sweden was quite war like, and left their blond genes in many a German baby. If the early Germanic tribes were blond, then Spaniards, Italians, and the French would all be very blond. The original Germanic people were brunettes. So, the Nazis were having babies with Norwegian women for the blonding of the Reich.