When you combine military prowess, scientific and industrial strength, national cohesiveness, demographic numbers and strategic location, it is clear, that in both world wars, all the world regarded the Germans as the single most fit 'race' on Earth.
So according to popular Darwinism's view of existence as being an eternal enlarged case of mortal man to man combat, with the best man always winning and the weaker man always dying, Germany was scientifically bound to win out.