I’ve heard people repeat a few theories for why Game of Thrones started so well and ended so badly. Most of these theories don’t make sense.

Theory 1: David & Dan are good at adapting books, but they didn’t know what to do when they ran out of book.

Seasons 1 through 4, which adapted the first three books of A Song of Ice and Fire, are up there with the greatest television shows ever made. Season 5, which adapted the fourth book and part of the fifth book, was mediocre. If this theory were true, season 5 should have been on par with the earlier seasons, but it wasn’t.

Furthermore, season 6 was better than season 5, even though season 5 was still based on the books, and season 6 wasn’t.

Even more, David & Dan wrote some excellent original content in the earlier seasons, such as the extended arc with Arya and the Hound in season 4 (see this scene, which wasn’t in the books).

Some people say, well they know how to write short scenes, but they don’t know how to write story arcs. Then how do you explain the famously terrible dialogue in the later seasons?

Theory 2: David & Dan were always bad showrunners.

I hear this one a lot. There’s some evidence for this theory—prior to Game of Thrones, David was best known for writing X-Men Origins: Wolverine (a famously bad movie), and Dan had no prior writing credits. But if they’re bad showrunners, why were the first four seasons so good? I can buy that bad showrunners might accidentally create a pretty good show, but I don’t see how they could accidentally create one of the best shows of all time.

Theory 3: David & Dan lost interest and started phoning it in.

This explanation makes more sense because it can explain the nearly-monotonic decline in quality. But it still can’t explain why season 6 was better than season 5. And the timing doesn’t entirely work out—people usually say this about seasons 7 and 8, but season 5 was clearly worse than the previous four seasons, and it seems less plausible that they’d lose interest that early on.

Theory 4: Good writing emerges through a mysterious process that no one really understands.

This is my favorite theory. Many occasionally-great writers can’t consistently replicate their success, writers can’t tell which of their works will become popular, and nobody fully understands what makes great writing. That’s why, for example, Jane Austen thought Pride and Prejudice was her worst book, even though it’s what she’s most remembered for. Or why The Matrix is my favorite movie of all time, even though I like zero (0) other Wachowski movies. (The Wachowskis are another example of artists who occasionally produce brilliant works and most of the time don’t, and it’s not clear why.)

Or why people used to talk about good art coming from a muse—you didn’t write that brilliant story, you just wrote down the words that your muse gave you, which is just a poetic way of saying you have no idea how you came up with it.

This is kind of a non-explanation: “the reason Game of Thrones was inconsistently good is because lots of things are inconsistently good and we don’t know why.” But at least it turns a localized mystery into a much bigger mystery about the general nature of creativity.