User blog comment:Belanderanime/Question about the 3 FUTURES, 10 000 dragons PLEASE HELP!!!!/@comment-84.13.159.42-20130707231158/@comment-7418318-20130707235955

In the current (third) timeline it might be possible that F-Rogues magic was able to manipulated them "through" the Gate and that he compelled them to come through, or the changed that Hisui made to the Eclipse Gate due to F-Rogues "advice" somehow attracked them.

But apart from either option being rather unlikely that still doesn't explain why they came through in force in the first (F-Lucy's) timeline.

Of all the people around the gate Zirconis tried to eat Lucy first. Maybe that means that Dragons are somehow drawn to Celestial Spirit Magic (which was part of the Eclipse Gate too).

While that's quite far from what I'd call a good theory, with the total lack of real information, I can't come up with something better right now.