User blog comment:Darkcloud1111/Good Idea, Bad Idea~Mountain Glenn/@comment-5217560-20141013022054/@comment-4010415-20141013035350

They reeeeeally wanted to expand.

I dunno, maybe at the time, Vale was overpopulated, and they felt that Vale really, really needed the expansion. So, even if the expansion meant living underground, it was still an expansion, and it was safe. At least, until subterranean grimm got in.