The Interview was never mentioned by the hackers until after the media starting running with the story
North Korea threatened war over this movie - http://www.bbc.com/news/world-asia-28014069
Now again, North Korea's words are kind of cheap, but they were talking about as big as you can get before this hack, and then specifically warned Sony to "obey" them. We have absolutely no idea what communications happened between the group and Sony and then law enforcement, so the whole what the media reported angle seems rather spurious. Sony/Law Enforcement, people who know more than us, seem to believe it was related to the movie.