A lot of that is true, but I don't think it's a wholly sufficient explanation. Unfortunately, the "master race" rhetoric served a tidy political purpose, as we

A lot of that is true, but I don't think it's a wholly sufficient explanation. Unfortunately, the "master race" rhetoric served a tidy political purpose, as well, even outside of Germany. Throughout much of European history, there hadn't been a great deal of "German" history to speak of. The peoples we currently recognize as German were fragmented across hundreds (at one point, thousands!) of independent polities and micro-states. These peoples were scattered across a large portion of Central and Eastern Europe, even after the unification of Germany as a nation-state. Hitler was able to play the "Aryan race" card as a pretext to invading and occupying any countries or territories that happened to have German-speaking inhabitants of any appreciable number (Czechoslovakia, Poland, and so forth). Interestingly, his phrasing started off as being more about the "German people" or "German folk." When he set his sights on other quasi-Germanic countries, like Norway and England, he talked about the "master race," a broader and more strategically flexible concept. The "master race" concept also won him a small, but vocal number of adherents in the UK and US, particularly among the upper classes, in which racism and eugenics had become fashionable for a time. No question Hitler's psychology was deeply troubled (and troubling). But it's tough to cleanly separate his personal beliefs from his political opportunism. He seemed to act upon each in almost equal measure.