Overall, we rate the American Thinker, Questionable based on extreme right-wing bias, promotion of conspiracy theories/pseudoscience, use of poor sources, and several failed fact checks. Low Credibility.

mediabiasfactcheck.com - American thinker

So this is an extreme right wing propaganda mill.

Opposed to anarchism, democracy, pluralism, liberalism, socialism, and Marxism, fascism is placed on the far-right wing within the traditional left'right spectrum. Fascists saw World War I as a revolution that brought massive changes to the nature of war, society, the state, and technology. Wiki

...Otto and Gregor Strasser did much to grow the party by tying Hitler's racist nationalism to socialist rhetoric that appealed to the suffering lower middle classes...(Otto saw it wasn't socialist and left after a while)

...In April 1933 communists, socialists, democrats, and Jews were purged from the German civil service, and trade unions were outlawed the following month. That July Hitler banned all political parties other than his own, and prominent members of the German Communist Party and the Social Democratic Party were arrested and imprisoned in concentration camps. Lest there be any remaining questions about the political character of the Nazi revolution, Hitler ordered the murder of Gregor Strasser, an act that was carried out on June 30, 1934, during the Night of the Long Knives. Any remaining traces of socialist thought in the Nazi Party had been extinguished.
britannica.com - Were the nazis socialists

So Hitler used the socialists, then merged with the right, and purged and murdered them out of the party.

Mussolini did start with the communists and he learned how to get people to listen to his ideas, but by the time he gained power, the communists that booted him out were forgotten.