The whole sport has become rotten to the core.
It's been rotten for decades. There are just more sophisticated methods of doping detection and paper trail tracking developed as time marches on, so dopers have to be in cahoots with many influential people and enormous, corrupt agencies who can supply them, cover up their transactions, spend a huge chunk of time testing and re-testing (e.g., Alex Salazar's testosterone trial runs) to see how much they can get away with, prepare cover stories/lies in advance and school people in ways to back up those lies, etc.
If any wrongdoing IS exposed, the grand scale of all this cloak-and-dagger sophistication makes things look even worse than somebody merely buying steroids and injecting himself, the way it was done in the 1960s. But the cheating has always been there. If today's doping techniques, methods for evading detection, and monetary incentives to athletes, agents and sponsors were present 50 years ago, you'd have seen sub-13:00 runners as soon as all-weather tracks became common. The level of competition today has undoubtedly provided us with MORE sub-13s than we would have seen back then, and some of them might be CLEAN, but some have been proven dirty. As with roaches (there are many more behind the walls for every one you see in the open), the fact that any dopers AT ALL have been caught, given how much energy goes into beating tests and given how ineffective the tests are against forms of doping like micro-dosing ... this only HINTS at the extent of cheating in the sport.