If it was a simple package intercept alone, there would be no way for them to link the suspect to SR, let alone link him to a certain SR profile, let alone getting access to private information on that profile (his transaction history, which I assume was given as evidence of the 11 alleged importations).
Either he gave up that information somehow (as the TOR browser doesn't save credentials), used a username he is "known" to use on the clearnet, or the more nefarious possibility:
It could be likely that Aussie feds set up a fake NL vendor account in order to set up a "deal" with that target. This would give them his real name and address (thus linking him to the SR profile) and ultimately establish PC for the raid. By sending him small amounts to establish trust (giving the feds evidence of the 11 "importations") they probably got him with a much larger importation charge then he otherwise would have gotten.
If they'd set up a sting involving a fake seller, it would be in their interest to publicise it. Our drug enforcement process is built around throwing the book at a few people to attempt to discourage many. If people thought that the seller they were buying off was likely to be a cop, that would significantly discourage SR buying.
(1) over 10,700 clear text msgs about drug dealing (2) announced to a forum probably watched by every police outfit in the world he was in Australia and about to start importing a lot of product and selling locally, basically inviting Aus feds to contact him and set up stings (3) imported drugs directly from a known drug exporting country (netherlands) through probably the toughest customs on earth who scan every package, who no doubt flag everything including envelopes from there for investigation.
I do like his defence of being the village idiot though. Seems to have worked since he's only getting 2-3yrs, which means 1yr and parole.
"Mr Jassar told Judge Murphy that Ms Ormsby was in court and that her piece – Silk Road: The eBay of Illegal Drugs – was the first views on the website by a journalist." lol Adrien Chen, your thunder stolen.