The truth is no one knows why they didn't bring those charges, or the real details behind the evidence or what happened in those interactions. It's pretty much shrouded beneath things like: -DOJ released some details and screenshots, but -the FBI agents who were involved in investigating this topic were like arrested for stealing bitcoin from silk road or something, so their work is hard to find credible -general lack of clarity as to the identity of the person running silk road at the time this happened