In the world of Toril, deities seemed overwhelmingly powerful, yet without their true forms entering, there were too many powerful beings that could stop or even harm these avatars or divine embodiments of the True Gods.
Moreover, it was not worth it for Coron to desperately lead the Elven Pantheon over such a trivial matter!
There were simply too many demons.
These forsaken territories, for the Elves, were actually negligible; Eternity Island was also nice, safe, and far from humans.
However, if one day the humans they once looked down upon managed to completely reclaim Elf King City and rename it as they had other cities, their prideful self-esteem would be somewhat unable to accept it.
Meanwhile, the number of Elves simply couldn't sustain such a huge depletion.
Coron, probably upon discovering the existence of the Undead Tribe, started considering the matters of Ferun.
He, too, knew about that prophecy!