Back in my audio engineering days, metal musicians were typically a joy to work with. Very professional, laid back, and cool to be around. There was an occasional exception, sure, but for the most part metal days were the good days.
Meanwhile some of the absolute worst to deal with were the happy joy musicians. Motivational pop (it was a thing), children's music, and happy pop/rock in general.
So the music that told people to feel good about themselves was often performed by continually angry, insufferable egomaniacs.
But the music that told people to unflinchingly stare into the void was performed by laid back, pleasant, seemingly well-adjusted people.
I have a theory that being able to get out frustrations helps us mentally adjust. But bottle it all up, even in music, and cover it in a "just be happy" sheen, and the dark ball inside will continue to grow.