Why did the changeling army choose to invade Canterlot during Princess Cadence and Shining Armor’s wedding? The answer can be found in a chance meeting between Queen Chrysalis and Nightmare Moon, back at the Summer Sun Celebration …
Following her defeat, Chrysalis visits Celestia in her chambers for a long chat. For all their differences, they also find they have a lot in common, some of which puts Chrysalis’ recent actions in a new light.
"Dear Princess Celestia, as your (former) most faithful student, I feel I have to warn you that this is probably a trap. Chrysalis cannot possibly be serious about this. Why would anyone, much less her, want to shoot a documentary on us?"
After the defeat of the changelings, Queen Chrysalis realizes that her remaining subjects may not make it back home to the hive alive. The question is, is she willing to pay the ultimate price so that they might survive?