There are many different species living on Arha. Dwarves are worshiped by other species just like Elves. With the ability of dealing with steels, Dwarves crafted almost every single weapon distributed on the continent. Since Dwarven weapons are valuable, even Emperor Barthol did not suppress Dwarves.
However, after Barthol finished unifying continent, he started to suppress Dwarves to eliminate chance of revolt. After Barthol vanished, Dwarves could grab freedom and created union and risen up to destroy Aurum to protect themselves from suppress of power.