Parson, my assumed answer to your questions has long been that it's an anti-happily-ever-after movement.
Many of us grew up on stories where bleak things happened (MC's parents died or tried to kill them, they are banished off on some quest or another, you know that conflict stuff that moves a plot out of once upon a time and into the story...) but ended (sometimes dissatisfactoraly) with "and they all lived happily ever after."
Then as we grew up we realized (some of us *coughme* belatedly) that life doesn't have happily ever afters. Prince Charming has ptsd after slaying the dragon, Cinderella keeps offending the servants by being independent and self sufficient, the little mermaid is ******* seafoam!!!
On top of that, we don't see "bad guys" getting much if any comeuppance.
The world is seen to exist in a series of grey areas.
So we get stories with anti-heroes, from the bad guys perspective, or that are just dark overall, because our view of the world has darkened, we worry about being someone else's bad guy, our armor is tarnished and dented which makes us feel more anti-hero than knight in shining armor...
On top of that 75 isn't many words to establish a world, set up a conflict, bring it to a climax, and provide resolution. I can shortcut by going dark which combines world building with conflict, and doesn't require much in the way of resolution.
*shrug* it's an unfortunate fact of our reality that hurt-people hurt people.
It's an unfortunate fact that the world we leave our children is not better, but worse than the world we received from our parents.
It's a hard fact that we can't let these unfortunate facts depress the hell out of us.
It takes a tough cookie to be truly positive this day and age.