Lots of things to unpack here. Porn, absolutely. Absent fathers, for sure.
I think one thing is, most men and boys have a deeply ingrained sense of fairness. This is why sports has been such an Achilles heel for the trans movement, because men see a TW athlete towering over much smaller female athletese, and they have a visceral sense that this isn't fair, and they flash back to that boy at school who used to cheat at games and how much they hated that boy.
But I think there's a related male thing at play, that if they feel the game is rigged against them, so they can't win no matter how much effort they put in, they'll just drop out. It's very easy for a discouraged man to hit a downward spiral.
Yes, the 80/20 thing has some basis in reality. The dating scene can be incredibly harsh on the man who isn't rich or good looking. I know lots of men who are long term single and don't have anything actually wrong with them, and lots of women wondering where all the decent men have gone and why they only meet creeps. I think a lot of those decent men, who I wouldn't call incel even if they technically are, have just given up on women and are spending all their time on hobbies.
I think what I see in incel-ish spaces is some of that, and a lot of adolescent narcissistic rage. Even with those who are technically past adolescence. They don't want to improve themselves, they think the world owes them something better than what they're getting.
Maybe a 50 year old man who can't get laid will find a certain level of contentment by spending his evenings making model planes. While a 20 year old man who can't get laid might join the SWP, where he'll be surrounded by bitchy women who still won't give him the time of day.
I hope model plane guy finds someone. What the young incel probably needs is generic dad advice, and he's never had anyone to give him that.
I always say, if there's an ur-text for understanding men today, it's Fight Club.