Fascism is described as both "Capitalism in decay" and as "Imperialism turned inward." It served and serves the bourgeoisie and petite bourgeoisie against the Proletariat and Lumpenproletariat, and historically arises when the Petite Bourgeoisie is facing proletarianization. That's why the most violently MAGA are small business owners and the like, and why they think immigrants are the ones proletarianizing them.
I highly recommend reading the first chapter of Blackshirts and Reds by Dr. Michael Parenti, which covers the material conditions surrounding fascism and who it served.
Most people are flexible, and if in the event there was mass success along Marxist lines or Anarchist lines, would join the successful movement.
And I am telling you that you can understand this "peculiarity" by reading Imperialism.
This is the most correct thing you've said. Hexbear isn't an org, it was described by one user as "not the Communist meeting room, but the bar they hang out at after the meeting." There are members of various orgs like PSL, FRSO, Food Not Bombs, etc. on Hexbear alike.