system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Despite both being highly totalitarian, how are Nazi Germany and Soviet Russia polar opposites in political ideology?

Nazi Germany was far-right and Soviet Russia was far-left. Despite this, both were highly oppressive, totalitarian dictatorships. What made their ideologies so unable to get along with?
gpt
Nazism was a nationalist movement, meaning that they were all about the (mythic, idealized) German people and German state. They were all about taking care of the German people first (and, obviously, horrible anti-Semitism and racism and so on) because they believed that Germany in particular was better than everybody else. 

Meanwhile, the ultimate goal of Communism is a stateless society where the working class owns the factories and stuff and there's no need for top-down control. In this philosophy, the Soviet Union was actually an intermediate stage-- basically, "we're going to control everything until you guys realize how great Communism is and rise up to overthrow all the other governments." (Obviously the USSR in practice would probably not have given up control at some future point, but that was the justification for its totalitarian governance.)

So Nazism says "GERMANY IS THE BEST NATION AND THE GERMAN PEOPLE ARE THE BEST" and Communism says "NO MORE NATIONS, ALL PEOPLE ARE EQUAL." Boom, ideological clash.