Is that as Greyhawk declined, torn apart by internal and external conflicts, the youngest prince gathered all of those loyal to him and sailed for the new world.
The new world was vast and staggering in it’s natural beauty and natural resources.
And, at the time, seemed uninhabited. Settlements grew to towns, towns grew to cities and New Greyhawk expanded westward.
In the year 1044, contact was made with a small group of Elven Niponese monks. They explained that a thousand years ago (when they were young men) the Niponese settled this land, but that “Beastmen” had surged over the eastern mountain and laid waste to their villages. Only the monks, in their hilltop temples, had survived.