Honestly, Stephen King is dead on here. One of the most effective tactics The Blair Witch Project used as a horror film was starting out as a seemingly normal documentary. At the time, the tactic was brand new, and made the audience feel as if what they were watching was factual. The found footage method made it seem like a total amateur job, but because of that, it also provided the illusion of authenticity. When horror feels real, it makes it that much harder for you to retreat to a safe space where you can internally tell yourself the monster isn’t real.