Introducing Shyamalan as a case history is interesting. I was actually listening to an old Writing Excuses podcast a day or two ago in which he was brought up exactly in this context, not delivering on promises. I think there may have been another element in that podcast. Shyamalan had this big mystery buildup and forced so much weight on what would happen in the third act, but the third act just kinda petered out and, on some level, was predictable. (I.e., the mystery wasn't some explosive reveal but just kinda one of those curling party horns, whatever they're called.)
The other thing Shyamalan suffers from is viewer expectation. I don't know if The Sixth Sense was his first film, but it is the first one I can remember of his, and I think many people fall into that category. Every time he puts out a film, people not only expect a twist, they expect him to top, or at least match, Sixth Sense. I think this happens to authors as well, when they hit it out of the park with their first effort. You set your own bar in that way, and readers are going to be disappointed if you aren't perceived as meeting it in later works. Sometimes, the perception of failure to meet it can be due to something as simple as a change in style or approach to storytelling--doing something differently from what your readers loved initially. When you connect strongly with readers, they want to feel that again in your next book, and the next one after that.
I think people want to feel the way they did in the Sixth Sense every time they watch a Shyamalan movie. Some of his later efforts seems to suffer from his trying to force the work to achieve that effect.