Communism and socialism were well thought up and defined by a philosopher, before anyone ever attempted to implement them.
Who was the philosopher that thought up and defined fascism, in a similar well-formed manner prior to implementation attempts? I don't think there was.
The word apparently comes from Mussolini's
Fasces of Revolutionary Action movement, founded in 1915, which eventually became the
National Fascist Party in 1921.
On the FRA wikipedia page, it says
"In 1915, members of the Fascio began to officially refer to themselves as "Fascists." They denounced Marxism, but asserted that they supported socialism, using the famous quote by French socialist Louis Auguste Blanqui: "He who has iron has bread" on the title page of its newspaper, Il Popolo d'Italia"
So, I think this supports my premise above. There was no such well-thought out philosophical foundation of fascism, underpinning it in the way that communism and socialism did/do have. Rather, it was more about a charismatic man wanting to do violence to bring about socio-political reform. Pretty much the same as Hitler and the National Socialist Party.
To what extent did either movement/organization/party strictly believe in the tenets of socialism? As opposed to whatever the political/power structure was in Italy and Germany post-WWI. I'm guessing, both were far more concerned with gaining power via warfare than how to make the world a better place.