A lot of people are missing why incels do this stuff, why they can't get a GF, etc.
If you look at a lot of their posts, especially this guy's, they tend to coalesce around nihilism. They believe their lives are meaningless, that they have no purpose unless they have a GF. Most of them are atheists, those who aren't have a highly exteriorized and moralistic form of religion that indicates only superficial belief and pure conformism. This causes them a lot of angst that they tend to exteriorize in lieu of sitting down and contemplating existence and purpose.
These guys hyperfocus on external problems rather than making an honest effort to build inner strength, willpower, and social skill, maybe this compounds a little bit with narcissistic superficiality. They earnestly believe women rebuff them because they're ugly, short, overweight, or dorky, so they start "maxxing" things as if real life is an RPG and women are NPCs with some kind of LOOKS check. They'll start "liftmaxxing," "looksmaxxing," and so on. They'll try to look like Chad, they'll buy designer -- equip the highest level gear -- but it always just amounts to making a more perfect turd, since the problem is what's on the inside.
Davison betrays his nihilistic illness himself: "There's nothing really to look forward to as an adult, other than getting rich." "I'm not advocating this, but if I have to I might even try and use drugs to make up for it, maybe cocaine fuelled sex or something, maybe that can make up for that missed teenage experience."
Failing to have any kind of transcendent, interior meaning really fucks a guy up. I remember having a nihilist phase until my mid 20's, and it really puts you in a bad spot internally. It causes all sorts of awful emotions to start welling up, and can turn into contempt and anger for the world. This existential angst is the same thing that caused the goth scene in the 90's. In impulsive and hateful people, like Davison, it becomes outright violence. There are a lot of people like this in the world where "God is dead." The absurdists pre-empted incidents like this, whilst also prefiguring existentialism. There were absurdist mass-killings.
The logic goes as follows: If there is no ultimate and objective meaning to life, then what sense is there in prolonging life, which is only a temporary episode fraught with suffering and comical agitation? A man is as good dead as he is alive, since the grave is his inevitable destiny. Hence, there's an intimate link between nihilism and mass violence. Life is meaningless without permanence, and permanence cannot be found in the cycle of life. If life is meaningless, then so too are other peoples' lives, as it were.
The solution to the incel problem is to beat nihilism. How that's possible is a matter of individual suitability. Religion can work, but it must be genuine rather than externalized. One needs a serious belief in God and must receive grace. The permanence of heaven can destroy any nihilistic embrace of the temporal. But, a lot of incel types are autistic and or hyperintellectual, hence why they get into right-wing political ideologies. I don't think that's because they're attempting to fill the void with politics, they're just inquisitive and divergent thinkers in some cases. Other cases might be explained by Luciferic "nazi villain" psychology, or a kind of psychopathic contrarianism. But in any case, they would have need of something intellective or esoteric. Theology, metaphysics, or an integral occult tradition could be a legitimate source of meaning for them. Buddhism, provided they can understand it properly as an ascetic tradition rather than a devotional religion, would be perfect. One of the aryan truths, Dukkha, which is that the world is suffering due to one's attachment to impermanence, diagnoses the issue. Perhaps even certain kinds of modern philosophy, like Husserl's phenomenology, could help them find some sort of transcendent meaning.
All told, the incel problem has little to do with "mental health" in most cases, but rather, spiritual health. These people are suffering from nihilism and it's causing hateful angst to well up from within, just like it did in the 90's goths and the absurdists so long ago. Finding meaning after the "death of God" is definitely hard, but it's the only way out for them. SSRIs, "maxxing," "a good ol' beating," joining the military, none of that will work, it will just cause them to further resent the world and externalize their inner angst. Incels don't need a beating, they need a book.
or puzzle pieces 
aren’t gonna kill you, 