Quote Originally Posted by Mihana View Post

Midgarsormr, the guardian of Silvertear Falls Lake brought down the massive dirigible but the cereleum on board ignited and caused an explosion that killed the guardian along with it. With that it either summoned or released the Primals which shot across the sky. Perhaps they'd had been sealed away, maybe they had been there to aid Midgarsormr with their power. Either way its death seems to have released them.

Since the dragon appeared, the empire chose to retreat from the realm.

With the emergence of Midgarsormr and the Primals the Empire retreated to form a new plan. They see the Primals as a possible threat against their plans to conquer the realm thus desire to rid Eorzea of these Eikons (Garlean term for the Primals.).
Perhaps the Garleans had captured those Primals but they were released when Midgarsormr destroyed the ship?

Apparently there exist Greater and Lesser Primals, and the Lesser ones can be Summoned by the Beastman Tribes (and eventually by us via Free Companies), so perhaps the Empire's original plan was to capture all the Lesser Primals because only they stood between the Empire and total domination.

What the Empire didn't count on though was that their actions awakened the Greater Primals (as well as us, "The Woken Ones) which stopped the Empire in their tracks. SO now they have decided to use Meteor to destroy even the Greater Primals or at least unlock the power of the Crystals in order to destroy the Greater Primals.

That is my guess anyway.