For the TNO I think it's the idea that nazis are cartoonishly evil. Their system is unsustainable, the unsustainability arises because nazis like murder, rape, and pillaging.
As for the nazi view on jews, subhuman ≠ low intelligence, in fact, the nazis really disliked IQ tests because they saw it as jewish propaganda and putting value in the wrong characteristics. For the Germans subhumans were non German. The more removed from Germans they were the more subhuman they were. Imagine less a white racist looking at a black man and imagining a monkey, and more like a space marine looking at xenos. Ultimately they were forced to pragmatize their view by giving honorary aryan status to several races, but instead shifting the definition of subhuman towards people who lacked what the Germans considered to be a proud historical and cultural history. Viewing the Jews as rootless parasites who feasted on the cadavers of great empires.
The nazis actually valued those of lower intelligence as long as they could be useful. Several fictional books written in the first half of the 20th century by authors that held nazi sympathies where the protagonist is rather dull but ultimately productive and competent as a settler or adventurer.