There is evidence that Kurt Cobian was an intersectionalist, and I suspect that he got radicalized into this extremist ideology by 90's third wave feminists, one of the earliest manifestations of the modern Regressive Left.
I theorize that because of his radicalization into this extremist ideology, he had become extremely depressed because of society's non compliance with Intersectionalism, which caused him to falsely believe that women and nonwhites were going to loose all their rights and did not want to live in this dystopic world that never came to pass.
Personally I think it’s mostly the other way round: self-destructive people with mental issues are drawn to the far left. “I’m feeling depressed because everybody else have been conditioned by Western society’s [insert any or all -isms]”.