Its about the Indians, they are getting revenge.
The hotel, the land that the hotel was built on, was ancient Indian burial grounds. The land was never theirs to begin with, they were only caretaking it.
Throughout the film the clothes suggest a patriotic stance for america. I believe Danny wears red white and blue for most of the film. The underlying cause of this insanity that Jack is destroyed by is this sense that he has always been there.
We as american's fight as though this is our land, as though we are natives, as though we have always been here. But we haven't and the movie is suggesting that true madness is believing such a thing.