The first fault is that even the studies done by Purdue prior to release did not indicate anything close to the 1% addiction rate they advertised, it was more like 8-12%.

The second, most Oxycontin users who aren't well off eventually move to heroin, because the effects are very similar, and the street price for Oxycontin is much higher. Ironically, where Marijuana was demonized for a nonexistent gateway property in the original war on drugs, Oxycontin was actually demonstrably a gateway drug for heroin.

There's a very well researched episode of the podcast "Behind the Bastards" hosted by Robert Evans that drills down exactly into all of Purdue's dirty little secrets surrounding Oxycontin. Once you realized just how many numbers were fudged, how many studies fiddled with, it becomes clear just how much had to be made to go wrong in order for this epidemic to really kick off. It's quite damning.