I think you are mistaken.
No action was taken? He has been the object of a three year political prosecution. Yes. It is a political prosecution. As I said earlier, no one (or virtually none)else (or virtually none) has been charged under this statute, and almost no one had ever heard of the "crime" of doctor shopping before Rush was tarred with it. It's been a long time now so I don't remember whether he checked himself into rehab before this all began or after, but the prosecution has gone on for years since he did.
As for "how did he get so much," others on this thread have explained that he really didn't have "so much." You just choose not to pay attention.
ML/NJ
No matter what you think of Rush Limbaugh. The cases are never pursued. They just aren't. It was only of interest to the DA & investigators because of the name of the accused - Limbaugh.