The depths of Arda hide many secrets. The titans were excavated just before the Great War, to serve as Arascus' greatest weapons. It is because of their existence that we needed to call on Tartarian Archdemons in the first place. Yet the dwarves kept digging. Through the endless black depths, what monstrosities they faced, we simply do not know.
I have to praise their loyalty out of respect if not anything else. The Holds were a nuisance until Rhomaion fell. Yet once it did, the dwarves started their retreat from the surface. Their grand armies turned inwards. Holds were once again left exposed. They began their endless excavation. We gave them trouble were we could. Some Holds were captured, but it was a tiny minority. No one was prepared to sacrifice hundreds of thousands of lives from their Orders for what would be a mere scratch on the underground kingdoms.