This is a fallacy of composition. Luck plays an important role in military success - Napoleon famously said he was less concerned about a general's skill than whether he was lucky - presumably meaning opportunist enough to seize an advantage when one unexpectedly presented itself. Likewise, numbers matter; a sufficiently large army will overwhelm many smaller ones not because of any inferiority of fighting spirit among the defeated, but just by being hopelessly outnumbered. Where small forces has famously resisted larger ones, such as Leonidas' 300 Spartans or the British Army at Rorke's drift, it did so because of the ability to exploit geographical or technological advantages
Your mistake here is to confuse a temporary strategic superiority that confers success in battle or even in war with some sort of moral or intellectual superiority. Back in World War 2 Hitler undoubtedly displayed strategic superiority at first (although the roots of German success go back to the late stages of WW1, when German generals 'banked' some of their military technology within newly Communist Russia, an arrangement which evolved into the non-aggression pact between Hitler and Stalin). But Hitler, like many conquerors before, fell victim to hubris and overreached when he should have consolidated. Despite being a political and military genius, his misplaced assumption of innate racial and cultural superiority (largely adopted from Prussian Kultur) proved to be a strategic weakness.
Your mistake here is to confuse a temporary strategic superiority that confers success in battle or even in war with some sort of moral or intellectual superiority. Back in World War 2 Hitler undoubtedly displayed strategic superiority at first (although the roots of German success go back to the late stages of WW1, when German generals 'banked' some of their military technology within newly Communist Russia, an arrangement which evolved into the non-aggression pact between Hitler and Stalin). But Hitler, like many conquerors before, fell victim to hubris and overreached when he should have consolidated. Despite being a political and military genius, his misplaced assumption of innate racial and cultural superiority (largely adopted from Prussian Kultur) proved to be a strategic weakness.