They’re each both Nazi and communist.
1. We Americans see both as being the same thing as far as we’re concerned. That’s the most important reason. Both are foreign-minded trash desiring tyrannical government. One is as bad as the other.
2. Both Nazis and commies were hard socialists.
3. The Antifa criminals would like to have the government own all businesses, land, etc. (commies), but they’re willing to settle for the government controlling all of the resources for a while (Nazis).
I find this rather odd since many antifa are anarchists. As we know anarchists hate government. In fact they want zero government so only the strong survive.