Compare the mass of malware that is out there with the level of technical sophistication, OPSEC to prevent detection, and precise targeting of its victims. Along with other big name malwares (i.e. Stuxnet, Flame, etc.), this class of malware is very precise in its objective. It isn't trying to make money for its owners. It isn't trying to replicate itself across the internet endlessly. Rather it has a key objective of infecting a specific set of networks. So when researchers call out the fact that it is likely to be "state sponsored", they are saying the purpose of the malware is very different than your average piece of malware.