They were created in 1970 and were ideologically marxist with the leninist spinoff. The story of how they were able to obtain weapons is very fascinating because it was what crippled them for years. Only when they got weapons they finally became politically effective.
Reason I consider them incel is because they had the equivalent of contemporary right wing doomerism, but they were left communist. Doomerism is about thinking all is lost and you are "forced" to live a life like an artist and be a romantic hero because what else you can do about it?
I mean its a mood defined by exhaustion where you feel the system cannot be redeemed and only meaningful responses are aesthetic and existential so you become heroic like anime characters and perform self-drama feeling like a hero. Today is the right wing that does it, they have the right wing doomer heroes like breivik, mosque shooter guy, the various killcels are more similar to anarchists.
In the past it was left communists with their fatalist view of "capitalism". And I dont believe in the existence of "capitalism" but this never made me stop being a fan of red brigades. Its all about underground life, sacrifice and feeling like a martyr and for sure a ton of incels can relate to that.
Obviously incels cannot relate fully because the hero martyr romantic type is a dunce. Essentially the hero romantic is a single minded person who believes reality to be absolute. To be a doomer incel right winger you have to believe your emotions are absolutely true, and you hate anyone who expresses an alternative emotional rationalization. You have to think "My emotional experience is objectively true" and what these people do is relate to each other on the internet and demoralize each other, they seclude into circle-jerks where they sing the same doomer tune.
Which is why the contemporary doomer, sadly, will never know others were like him, others were heroes and they were incel in the past, its a cyclical situation. All incels think they invented inceldom. There were always resentful bachelors and socially isolated intellectuals and misogynists around the world and they already created groups and all of them gave priority to their relatable emotional aesthetic experiences.
Live, blossom, blow up like a flower its the life of the romantic hero. All heroes are fragile like a flower, but they are as unaware as a plant. I always found them beautiful because they become very pure as humans. If I was spiritual maybe I would call these people "holy", like in islam they have the holy warrior idea, they also write poetry about these heroes. An incel islamcel wrote a poetry for me, he was sayng all stars in the sky are heroes like ER and unfortunately I cannot remember it precisely I should have screenshotted it.