The big difference is international vs national.

International communists/socialists were becoming very popular in Germany and the end game was to destroy German history, tradition and culture(as done in Russia). National Socialism was created as a reactionary ideology to the popularity of communism. It took pages out of the playbook of marxism but subverted them to enforce and preserve German history, tradition and culture.

Fascism is the antidote to communism. You cant combat an enemy that mobilizes the entire force of government, media, and military by being a good little libertarian and saying 'let the people choose' - the people have already been indoctrinated throughand through by massive organized power and money. You need to push back with equal force to stand the slightest chance.