>>28139850at this point i'm only explaining how their existence is being discovered. the reason behind spawns anywhere else is probably irrelevant. it's already been established.
perhaps if specific evolution traits interest you about a certain region, look towards the dex entries and try to make links to the overall theme of the region.
for example, the escavalier/accelgor evolution is a reference the the polarizing theme of the region and it's values/beleifs. ie: only through understanding do you gain strength.