I don't think its insulin.
Yeah, everyone is on it suddenly, but it's been around for 15 years.
Maybe it's just the fact that the internet has brought BBing everywhere, so the guys who really are genetic freaks - the Brewers, the Locketts, Evan, etc - are more likely to be found and start young. As opposed to playing football in high school, they're bodybuilding from 9th grade and are credible threats by age 21. back in the day, there were phenoms- Shawn and levrone for example.
Maybe there is something new, but I doubt it. More likely just more people exposed, and thanks to the web, guys can buy all the pieces to the formula, not just what they can get from a guy at the gym. instead of taking orals when you can get them, guys are doing pro stacks at age 16 with hgh, insulin, test, etc.