User blog comment:FairyRaven/Fairy Tail Chapter 325: Unity, Review and Commentary/@comment-5598380-20130329110449/@comment-7418318-20130329110929

That's also what I think. They opened a door to the past and the Dragons highjacked it to invade.

That would explain both why the castle is crumbling in Charlas vision (the dragons tearing out of the castle and leaving it so wrecked that it collapses) and why Lucy would close the gate (to prevent even more dragons from coming through).

In other words, in his attempt to prevent Lucy from closing the gate, he might have become the reason why Lucy was in a position to do so, since without his interference she wouldn't have been close to the gate.