Hypothesis: what matters here is a social toolbox for engaging with “attractive”/compatible women in a non-romantic/sexual way.

I.e. someone who, even as a teenager, had lots of female friends, is likely to have a learned how to deal with them beyond “I’d like to hit that”, but just as persons.

(Paradoxically, such a person is more likely to find a romantic partner, because they might have lots of M-F acquaintances/friendships that can potentially become something more.)

Someone who never learned that can only interact with (to them) attractive women through the lens of “I’d like to hit that”, which has a much higher risk of ending in failure.

If someone in the second category was always raised on the values of romantic success being a requirement for a non-failed life, and possibly with a touch of chauvinism/misogyny, they might wind up caught up in a frustrating loop of failure.

This is how incels can happen.