Hitler had a theory of why Jews had to be destroyed. He didn’t come up with it all on his own, of course, but relied on a poorly understood Darwinism and, later, on the ideas of the famous philosopher Carl Schmitt.
“Nature puts life forms on this planet and then sets them free in a struggle for power,” Hitler wrote. For him, everything that allowed humans to be closer to their “natural state” was good. Everything that distanced them from the state of “natural wildness” was bad. We should all jump at each other’s throats like wild beasts and allow the fittest to survive in this eternal struggle.
Why don’t we do this kind of thing, though? Why don’t we try to murder everybody we encounter in order to take away their possessions and resources? We don’t do that because we are organized in societies which are ruled not by “the law of the jungle” but by legal, ethical and moral norms. Even if I could kill my neighbor to take away his land and expand my own backyard as a result, I wouldn’t do it because I believe it’s wrong to kill people.
These moral, legal and ethical limitations placed on our desire to slaughter the neighbors and take their land or resources were, according to Hitler, created by Jews. Jews had no land of their own. In order to live on somebody else’s land, they needed to break people’s animalistic attachment to their land, and that’s why Jews came up with complex ethical, ideological (such as Communism), religious (such as Judaism and Christianity), etc. systems that limited everybody else’s power to engage in the “survival of the fittest” contest.
The greatest sin of Jews, according to Hitler, was convincing humanity that people were better than animals. Jews, said Hitler, imposed the dominance of reason and abstract ideas over brute force and animal instincts. Only the complete destruction of Jews would remove the temptation of this seductive idea of human primacy over the world of the jungle.
P.S. In case people don’t know, the reason why Jews were associated with the world of reason and abstract ideas lies in the nature of Judaism and the relationship of Jews with the Torah that Judaism mandates.