Because it's a ploy. Sony is in the business of making $100s of millions by making up story lines.
Who knows, maybe the threats to take The Interview down were real. If that's the case, it's probably because many hackers are anarchists, and many anarchists truly believe their the new age freedom fighter. Many have such hatred for the US govt and its policies, they sometimes are sympathetic to NK, and sometimes even favor NK policies. That's probably more plausible than the "advanced NK cyber army".
Implying that anarchists actually approve of North Korea policies...which pretty much is a dictatorship.
Let me guess anarchists also want to burn everything and loot stores. Am I right?