You're talking about only the USA. Actually, violent crime spiked in late 80s and then was coming down from that spike in the 90s, so there's that confounding factor. Most of the crime in the late 80s was juvenile crime in fact. It might have had to do with the culture of the time (inner city gangs, etc.)
A better way would be to compare what people focus on / use on a daily basis today vs in the 80s. If you are restless today you can pacify yourself with a mobile phone. In fact it's an addiction that gives you a boost of dopamine. And the virtual world is much less .... physical and violent, which reduces people's tendencies over time.
Another great pacifier of the 20th century is consumerism. Feel bad? Buy an ikea, veg out in front of the TV. There is a great documentary about how the PR industry was invented and Freud's theories about the "collective ego"
I'm talking across the industrialized world. The availability of the internet and other 'pacification networks' may be a contributing factor but it's clearly not the driving force.
Anecdotal, but growing up in a generally low-income rural area, I don't remember any of my peers not having a computer in the early 90s. Many of them, including myself, even had computers into the mid-80s and some of those families were quite poor, even by local standards.
The internet came later, but games like Doom were huge long before that, which is pertinent as you mention violent crime specifically.
