It Hydaelyn sundered herself, why doesn't First Hydaelyn handle the flood of light?

[Katish]

Also a possibility: each Hydaelyn from a reflection that saw demise just gets absorbed into Zodiark. So if by the end of it, if the Ascians achieved their goals, Zodiark could have theoretically become even stronger than it was once formed because it has all this transient aether. Leaving Hydaelyn in a much worse state than when she was, by not having her reflection returned and having to fight off the more powerful Zodiark as mentioned above.