That which is commonly referred to as the dwarven race isn’t strictly speaking a race at all. Rather, the dwarves are the fruits of the Giant Rock Marshal which is a mushroom belonging to the Marshal Mushroom family.
Dwarves, being what they are, were originally content to stay at their digs tending to the main fungus the gave them birth. Then they disappeared, became nearly extinct and now they're back again.
Notes about the peculiarities of this particular version of the Marshal Mushroom.
What drives the dwarves to venture out into the world and do the things they do.