Usually, fan theories explain some minor mystery, or something that's inessential to the plot of the show. Even though Jon Snow is Daenerys' half-brother, that doesn't really change the fact that the White Walkers are going to annihilate everything in their path.
This Westworld theory is different. This Westworld theory is what we in the industry like to call "a humdinger." Redditor NoMereVeneerOfVanity pulls together disparate threads to weave a tapestry that says, "Dolores is Wyatt, she killed Arnold, and she's wandering alone in an attempt to find out what happened."
It's a lot, we know. The theory makes several points, including that William is the Man in Black, and introduces some reasoning about timelines. After introducing the concept that Dolores is Wyatt, and responsible for the town massacre, the redditor drops a serious bomb.
"During the massacre, Dolores killed Arnold. Arnold's death occurred at the same time as the massacre, and maybe the massacre even resulted from Arnold's work on Dolores. Dolores is somehow linked to Arnold more than any other host, and it may be the case that Arnold told her to kill him, or got her to kill him, to prove that she is conscious and solved the maze. Ford wouldn't say that he and Dolores are friends 'at all' because she is either the host that killed his dear friend, or the creation of his arch nemesis that he can't seem to crack."
That's interesting, but the redditor then introduces a unifying theory of a single timeline, which links everything together in a robo-hallucinatory way. Reader, our collective mind was blown.
"When we see Dolores in the William timeline, we often see her trip out for a few seconds. Sometimes these show past versions of herself dead, showing that she got this far in the maze before but hit a literal 'dead end.' Sometimes we see Dolores remember things that are obviously in the past, like the Wyatt massacre. STILL OTHER TIMES though, we see Dolores more or less doing the same thing that she's doing with William, except that William isn't there. THIS is when we see Dolores as she is, in the present. She is mirroring the path she took with William to bring her to the center of the maze (the Wyatt massacre town) in order to assume the mantle of 'Wyatt' and become the villain that Ford knows she can be."
We'll take it a step further. Why not?
Ford would want to send Dolores down the road into Wyatt-dom after instituting the Reveries system because he wants to unravel the mystery of the maze just as badly as does the Man in Black. Why? Because he doesn't know what happened to Arnold any more than anyone else does. If Arnold was the key to the creation of the hosts, then Ford would want to know what had happened to him. Similarly, if he lost his friend but never knew why or how, he might spend a life searching for answers. So he rebuilds parts of the long-buried town where the hosts were programmed and Arnold was killed and sends Dolores off her loop and towards the site of her greatest sin. When she finds the town again, she'll reveal to Ford the thing that has haunted him for years. She's tried to go back before, with William, which is why we're seeing his backstory. And now, later, he's going back with Teddy to try to solve the maze that Ford has left for him. Maybe it's his parting gift to an old friend. Or maybe he's giving his longtime boss the middle finger of a lifetime.
Finish picking your brains up off the floor and read the rest of the theory here.