Since rule of subreddit is no personal information I wont link original pdf. Instead I will just post important three points from document that explain how and why he got caught.
Investigation lasted since 2015 until august 2017.
40 . After observing the bitcoin ''tip jar'' advertised by [nickname mod used] agents conducted analysis of the incoming and outgoing transactions from that bitcoin address and learned that 15 out of 17 outgoing transactions from the [nickname mod used] tip jar went to multiple wallets controlled by [EU County] national [Full name and surname] on Localbitcoins.com.
41 . Open source data revealed that [Full name and surname] has lnstagram and Twitter accounts. Agents compared the writing style of [nickname mod used] on [Name of dark market] forum while in Senior Moderator role to the writing style of [Full name and surname] on his public Instagram and Twitter accounts. Agents discovered many similarities in the use of words and punctuation to including: the word "cheers'' double exclamation marks; frequent use of quotation marks, and intermittent [EU County] posts.
and.... final mistake
42 . On August 31, 2017, [Full name and surname] travelled to the United States for the first time to attend an international beard competition in Austin, Texas. A border search of his laptop upon his arrival at Atlanta International Airport confirmed his identity as [nickname mod used] On his laptop was the TOR browser, apparent log-in credentials for Dream M arket, $500,000 worth of bitcoin, and a PGP encryption key entitled ''[nickname mod used]'' which matched that advertised as [nickname mod used] on [Name of dark market].
mfw
to attend an international beard competition in Austin, Texas
Probably first guy owned because trying to attend beard competition
Here is few years old video from CCC 29C3: Stylometry and Online Underground Markets (EN)
https://www.youtube.com/watch?v=zkh7dwwfrHM
(Stylometry is identifying author of anonymous post based on writing style.)
If moderators allow I can give name of Darknet market that was involved.
[EDIT] adding link to pdf: https://linx.li/oxymonster.pdf
This was posted without the redacted much earlier today.
Cheers!