So, what's the story behind Azys Lla?

[BubblyBoar]

It was pretty much put into the air shortly before the fall of the empire. So anyone still on it, provided they were when the quake hit, came back to ground and lived life as they could. Destruction of the empire isn't death of every single citizen within the empire. But it does me they lacked the resources to continue the empire or felt that it would not be a good idea to try and raise that empire from the dust of the quake.

[LystAP]

It was pretty much put into the air shortly before the fall of the empire. So anyone still on it, provided they were when the quake hit, came back to ground and lived life as they could. Destruction of the empire isn't death of every single citizen within the empire. But it does me they lacked the resources to continue the empire or felt that it would not be a good idea to try and raise that empire from the dust of the quake.

If I recall, the floating continent wasn't precisely self-sustaining; at most, it depended on supplies from the ground, of which was cut off when the empire fell. They probably descended with what technology they had, and once on the ground, had to deal with a whole variety of issues that inhibited their return.