To be fair, now FBI deserves some of the blame. I'd like to see exactly why they believe this was a specifically Korean thing and not a "North Korea used this same malware family they acquired elsewhere for their South Korea attack earlier" situation.
To be fair, the FBI is a big organization which employs many intelligent individuals. It's very unlikely we know everything about this situation that they do.
http://www.fbi.gov/news/pressrel/press-releases/update-on-so...
Proposed Scenario:
FBI hamfistedly assumes B -> C, not A->B and A->C.