Because in US money speaks:

Between 2006 and 2015, Purdue and other painkiller producers, along with their associated nonprofits, spent nearly nine hundred million dollars on lobbying and political contributions—eight times what the gun lobby spent during that period.

And the revolving door:

He had also enlisted Rudolph Giuliani, the former mayor of New York, and his associate Bernard Kerik to preëmpt any government crackdown.