If any one thing can be said to have created the incel problem, it's the internet. Incels are terminally online and wallow in misery at every opportunity - their own, or one another's. They alternate between blaming their own looks for their failure and blaming women for refusing their advances, without realising that what's actually causing the problem is the fact that they spend all their time hooked up to the internet, obsessively strategising how to get laid, rather than just going out and enjoying life.
Incels are the toaster fucker problem with a different coat of paint. Back before the internet, if you couldn't get a date, you'd get mad, people would tell you to grow up, and you'd eventually just chalk it up to a dry period or realise that you were being weird. Then you'd get over yourself and marry a sweet girl who had a nice laugh, which you'd hear a lot because she found your lame jokes funny, and could carry a sheep under each arm. Today, if you can't get a date, you go online and find a bunch of other men who can't find dates, and who tell one another that it's all chad's fault and women are all whores, while obsessively trying to craft your face and body to match an impossible ideal form in the hope of catching a supermodel's eye. All the while you'd spiral ever deeper into angry fixation on the thing you can't have. It's just troonery without the genderwoo, which is why the incel-to-troon pipeline is so powerful.