He probably under-rated the intelligence of the people who might confront him in the USA. There seems to be a general tendency to under-rate Americans (hopefully this will continue). If he would have had the stuff shipped by various companies in small amounts, he might have been able to get away with it.
This reminds me of the German hackers who tried to hack into American national security computers. They did not know of the former astronomer who was working for the government and caught them cold. The German hackers probably either thought that nobody was watching or that they could easily defeat the people who might be watching. They ran into somebody who possessed considerably more training and experience then themselves.
The United States, by the way, has hacked into al Qaeda's website alneda. The page now says something to the effect, 'Hacked, tracked, now owned by the USA.'