Drugs addict, i believe this 2 bandits need money for drugs.They never think about 10 years in prison for their crime, they only think how to get money fast and easy.
Drug addicts desperate for money normally don't show this type of sophistication. In this case, these two goons worked out a well-planned operation, and managed to convince the victim to do trade with them. They also selected their victim wisely. They chose someone who is inexperienced, and less likely to report the crime to the cops. Also, they knew that it is difficult to prove the theft of Btcoins.
the whole thing sounds like a drug deal ~ maybe the deal went bad somehow and they split with his coins? who knows anything is possible!
+where did he get the bitcoins to begin with? Being an underground currency dealer is a tough job! ~ Especially in NYC ! lol 