My guess....
Watching this happen over the years, here's my guess of why it's exploding.
It's American culture.
The average American seems to want something for nothing. We glamourize violence. We say it's illegal to talk about God in the classroom but it's okay to talk about "alternative lifestyles" and sexuality. If religion is something reserved for the home and church, when did the birds and the bees suddenly become the perview of public education?
The only morality imposed in American society is the lowest common denominator. While I don't begrudge Tupac from his success, that a criminal can become such a public icon (God only knows how far that influence worked on young minds) doesn't bode well for our society. Remember when our childhood heros were people of virtue? Role models to live up to? Now we get Tupac, Bill Clinton, and the like.
Going back to prison population.
The common thread is that without morality, there is no respect for the law. I don't like what the laws say on many occasions, but I obey them because that's the moral thing to do. If a law is that bad, I fight to have it changed or recinded.
The average American thinks nothing of lying to get something they are not entitled to. The average American sees nothing wrong with breaking the law so long as nobody really gets hurt and they get away with it.
Sadly, a lot of people get caught, and if we don't punish them, it's going to become Hell on earth. So....lawlessness abounds, and prison populations explode. The solution isn't more prisons. The solution is a return to morality.
Beating up a guy over a dispute is not the way to solve the dispute.
Killing a person for anything but self-defense is not right.
Raping someone for sexual gratification isn't justified.
Selling drugs to make a living isn't right especially when you're pushing the really bad stuff. For the lesser things, push to change the laws, don't whine about getting caught.
Don't have the things you want? Get a job and earn them. Don't jack someone else's stuff to get it for free. Otherwise, learn to be happy with what little you have.