Something I’ve always wondered is what kind of women were in the lives of incel men when they were young. Did they have a bad relationship with their mother? Did they lack sisters or other female family members? Or is their family situation irrelevant? Maybe some particular situation in their early years caused them to develop a complex around women?
Adding this link, though it doesn't seek to answer the "why" as much as describe the "what"
https://www.cambridge.org/core/journals/bjpsych-advances/article/incels-violence-and-mental-disorder-a-narrative-review-with-recommendations-for-best-practice-in-risk-assessment-and-clinical-intervention/6A934637D21AEE4C1D90FAF5FB63D769
I can't copy/paste from that soutce on mobile, but it mentions many respondents to a questionnaire indicated they lived with their parents and had either depression, anxiety, or autism (prevalance in listed order).