When your once-fertile mind is now in a rapid, unprecedented creative freefall, like M. Night Shyamalan's, for example, you can't afford to sit idly by and let your few remaining ideas, no matter how terrible, drift away while you concentrate on making a shitty adaptation of a NickToon. What if this is your last semi-coherent film plot before everything fades and you can only think in twist endings?
Thus, when Shyamalan recently had the thought, "Maybe some people are stuck on an elevator, and maybe one of them is Satan (who maybe looks like a nude Darkman?), I guess," he quickly passed the idea on to screenwriter Brian Nelson and directors Drew Dowdle and John Erick Dowdle before he could forget it--or at least while he's still allowed to put his name on a film. And now we have this:
Maybe I'm wrong, but assuming one of these elevator passengers is literally Satan, I'd say smart money's on the weird looking guy in the suit who's married to a beautiful, fiery-haired, supernaturally-proportioned woman.