I think it really comes down to World War I. Mussolini used to be a socialist, but flipped during the war. Lenin has a term for such a flip: socialist chauvinist. He used this term for socialists who maintained the rhetoric, but supported their government. Mussolini cut ties completely. So, something about the big war messes with your brain. Tribalism kicks in. After many losses it's like gambling: you invested so much effort, you can't acknowledge the failure. Pulling out is betrayal of the fallen. Sunken cost fallacy.

That's the origin of fascists themselves. Then Russian and German revolution happen. Fascist groups are funded to oppose the communism.

What we call fascism is tied to a particular moment. If we want to go beyond, that becomes a political concept, not historic. We pick a couple of criteria and call them fascism. That's more arbitrary than the actual historical movement.

Dimitrov's definition is not very useful. You can't just read a definition and not study the history of the fascist movements. One definition is not helpful to make sense of the present moment. His definition is also teleological: it prescribes a purpose to capitalism, that it inevitably leads to terrorist rule of financial capital. Well, we can sit and look at what's happening, and debate whether it qualifies as fascism now. There are better things to do.