Bahamut and Tiamat are Popularized

Religious event

Quite simply Bahamut and Tiamat become popular around this time from a religious perspective.

It is known based on infomation in the hole that before the dragon gods became popularized from a religious perspective a group of Azarkeans were at some point affected by some kind of magic and a group of Avian people would then bring about the first dragonborn.   Unfortunately that is about all that is known more or less from what I can remember at least.