Motive
Even if everyone could hack anywhere one would need to have a motive, and that, or the rewards, need to be great enough to override the risks of being caught or blamed.
I don't see North Korea having the motive. I don't see what they actually gained, or could possibly have gained, from such a hack. This poorly rated film was no worse than what North Korea and her leader has slung at them every day.
It still looks more likely to me that it was script kiddies doing what script kiddies do, perhaps a western false flag to get crap thrown at North Korea.