I once read a detailed account of how he was caught. It seemed like the kind of clues that you could only connect post-hoc.
It seemed like parallel construction [1] to me. Considering that the NSA is known to give the DEA "tips" [2], and has a division specifically to start parallel construction investigations [3], and this was a high profile drug case, it would be odd that they didn't use parallel construction techniques.
I read the book about it, and it was actually an IRS agent who found a super old forum post where the guy announced he had created the Silk Road using a username that was easily linked to his real name.
The IRS guy figured it out and nobody would act on it because they all figured the FBI would know better and they should wait for the FBI to do it right. ... but actually he nailed it.
It seemed like parallel construction [1] to me. Considering that the NSA is known to give the DEA "tips" [2], and has a division specifically to start parallel construction investigations [3], and this was a high profile drug case, it would be odd that they didn't use parallel construction techniques.
[1] https://en.wikipedia.org/wiki/Parallel_construction
[2] https://arstechnica.com/tech-policy/2013/08/us-drug-agency-g...
[3] https://www.reuters.com/article/world/exclusive-u-s-directs-...