The Dwarves were the cunning side. For every Huffle Bandileggs down at the Drum, there were many Low Dwarves still around. They were the ones who knew exactly where to dig so that the tunnel wouldn't collapse... and so that it did.
Trolls weren't the best of thinkers. Patented fan-cooling hats aside, Ankh-Morpork was not ideal for silicon conduction. But trolls were strong and knew about fighting.
The Dwarves always won. Any kid knew that, but they were wrong. It was all a matter of how you played.
Just because it was a game didn't mean it wasn't true.