Under the Dome/WMG

We are the alien children.
Think about it: the alien children are observing the terrible fate of Chester's Mill, for their own entertainment, and only make the arbitrary decision to remove the dome when the characters have, in a sense, earned their happy ending. Let's face it: the dome vanished at about the point you were also ready for it to go away.
 * I had the exact same thought while reading the book.

The Alien children are Eldar
Sounds like the kind of thing that they would do, if they can create a god of lust, messing around with a single town isn't that much of a stretch.