Marx believed in the supremacy of the international proletariat, the industrial working class of the mid 19th century that was nearly nonexistent by the 1930's. The Nazis believed in the supremacy of a Master Race whose blood conferred the ability and the right to rule. The former believed in solidarity by economic class, the latter by racial identification.
Both are "socialist" in the collectivist approach to individual political and property rights but are economically different - Marx would have claimed that they were different stages in the inevitable historical progression toward world socialism. Communism, however, requires the State to possess the means of production, and Nazism allowed private possession of them so long as their use was directed by the State. In that Nazism more resembled fascist economic practice than Marxist.
These doctrines were similar in practice - both Nazism and Communism employed the rhetoric of oppression and offered moral absolution for the violent repression of race or class enemies, respectively. As Hayek pointed out, it was common for Communist street-fighters to join with their enemies in the Sturmabteilung once it became clear which side was going to win. They had, after all, common enemies.
This gets very confusing when one attempts to trace the roots of Nazism from its contemporary fascism. The latter, codified by Mussolini and a fellow named Gentile, was nominally anti-communist, even anti-socialist although its own economics were difficult to tell from socialism in practice. Nazism and fascism were nationalist; Marxism is emphatically internationalistic. All three are statist (Marx proposing that eventually the state would "wither away," one of his more nonsensical and historically invalid notions). All three are collectivist. All three posit the supremacy of the collective entities over those of their individual constituents, the difference being the nature of those entities. All three were and are murderous, brutal, and in application thoroughly oppressive and evil. But identical, they were not.
Huh??????? If anything, it was 10 times bigger in the 1930s.
> (Marx proposing that eventually the state would “wither away,” one of his more nonsensical and historically invalid notions).
Maybe Marx put that notion in to get support from gullible anarchists, do you think?