I want to know what makes third acts so difficult to pull off in any medium.
Warning: some *SPOILERS* below.
So for instance, Chris Nolan's The Prestige
is ostensibly about the three act structure of a magic trick/illusion, but can also be interpreted as a metaphor for filmmaking. A character in the film states that the "prestige" of a trick, or third act, is the "hardest part" to pull off. This has always stood out to me because Nolan's films have often been criticized for having weak third acts. For example: The Dark Knight
is overall a very well-received movie, but what criticism is levied against the film seems to be focused at the third act (i.e. the ferry scene, or the showdown with Dent/Two-Face seeming like a tacked-on climax). This is also true for The Dark Knight Rises
: I know many people feel like Nolan fudged the "prestige" of revealing the child of Ra's Al Ghul and the overall climax of the story. I can think of other films that I really enjoy up until the third act when there seems to be a dramatic shift of tone, or just disappointing resolution of plot points. And then if you consider the third entry in a trilogy to be the third act of a story there are more examples: there is a prevailing sense of "third times the harm" regarding many film trilogies. Examples off the top of my head: the Godfather part III, Spider-man 3, X3, the Matrix trilogy, Alien 3, the aforementioned Dark Knight Rises, Back to the Future III, Mad Max Beyond Thunderdome (which I love, but it is often compared unfavorably to The Road Warrior), and I've never heard or seen anyone seriously proclaiming Return of the Jedi to be superior to either Star Wars or Empire.
I know long-form or episodic storytelling differs from the traditional three act structure, but there are also examples in TV storytelling where the writers set up situations beautifully, but then the resolution of the plot is unsatisfactory for many viewers. Recent notable examples include the finales of LOST and Battlestar Galactica, though I am sure there are many others. While this phenomenon may not be directly related to the difficulty of executing third acts of stories, I feel it might be a related phenomenon.
So my question is: from a narrative, dramatic, storytelling, or other perspective, what makes third acts so difficult to pull off satisfactorily?