Silk Road was, at its height, uniquely successful and making an absolute mockery of the United States government's capacity to regulate drug trafficking. In addition, he fashioned himself an anti-establishment persona, going by the handle "Dread Pirate Roberts" online.
He was unique in his magnitude of success. Governments can successfully magnify their enforcement ability by making an example of outliers.
It was a forum that mocked the government's ability to regulate drug trafficking and therefore he was prosecuted?
I find that hard to believe.