Your typical incel is that quiet guy in school with bad skin, plain clothes, and oily hair, whose only friends were the other outcasts. Like everyone else, they just wanted a normal relationship with a normal woman. It’s the repeated failure to form those relationships that leads to the resentment and anger we now see. They weren’t always like that. The bitterness and hatred is a coping mechanism for their situation, not the cause of it.
I’m sure that’s true in some cases, but I wouldn’t generalize it as the explanation for most incel’s situations that they simply had too unrealistic standards