You know how there's that internet group Anonymous who go around doing random white knighty stuff, mostly for no particularly good reason? And any other number of groups of script kiddies who like to stir up 🤬 on the internet just because they can, not unlike the other big Sony hacking back in 2011?
Maybe it was KJU and his army of hackers. Maybe it wasn't. It probably isn't KJU making threats to bomb cinemas (because why would you potentially start a war against the US over this, which is what a bombing on US soil would amount to), so there's at least one other group out there with an interest in people not watching the film.
Don't ask me why anyone else would want people not to watch it. Some people are mental.