Hang on, the story ends with the Doctor radically changing his past. What we see near the end isn't what originally happened; the War Doctor originally used the Moment by himself, and burned Gallifrey. But earlier on, we see that Eleven remembers some of what's going to happen, so it must always have happened....YE GODS, I'M SO F***ING CONFUSED, SOMEONE PLEASE HELP!!!!
And what's the deal with the Curator looking like an older Fourth Doctor? Is that supposed to mean something?
In a sense the Doctor did use the Moment to end the time war, just not in the manner in which we were led to believe.
He had activated the Moment in order for the consciousness of it to appear. Don't forget the implication was that the Moment judged who could use it or not. So it made sure that The Doctor used it in a manner inkeeping with the personality of The Doctor.
Previously it was just an assumption it was a big red button that obliterated the Dalek fleet and Gallifrey. When in a way it was the Moment using The Doctor to end the Time War.