There were fewer people, and not as easy access. Now we have more people,, and many, many more guns. And many, many more ways to buy guns.
And I don't think we have more disaffected people now, necessarily, per capita. I think we have more freedom and freedom of movement. I think what decades ago were fantasies of killing the bullies and the pigs now have become realities that can be realized by anyone at all.
AND
I think people see it as a way to become famous. To become somebody, in this huge world, when they feel like nobody. Yes, I think we can point to the internet for exacerbating that.