Aside from megalomania, Hitler invaded Russia because he loathed the Slavs at least as much as the Jews. The fact that Russia was Communist then was simply a bonus, as far as Addled Adolph was concerned.
It’s worth noting that Orwell’s Homage to Catalonia documents his nearly getting caught up in a purge by the Stalinist Leftists in Spain, while escaping from the country, because he had been fighting against the Spanish nationalists / Fascists with a different Marxist faction. Despite being in the middle of a full-blown civil war, the Leftists were still infighting among themselves in a deadly way.