Seriously.
The Gorons underwent a huge personality change in Twilight Princess -- they went from peaceful idiots to angry-looking peaceful idiots. And, while their elaborate mines were pretty awesome, they didn't seem to serve any purpose...like...at all. Gorons don't need to mine for stuff. They just eat. They eat rocks. I can't help but think that they were just eating whatever they were mining for.
They aren't smart.
Herr hurr I keep changing the way I draw Midna.