The Mavericks gave it their best effort, but the Thunder's talent won out in a Game 3 blowout.
The Oklahoma City Thunder are really talented and good at basketball. The current Dallas Mavericks aren't so talented and aren't so good at basketball.
Sometimes, it's as simple as that. The Mavericks did a lot of things wrong tonight -- couldn't rebound, couldn't defend the pick and roll, couldn't generate decent looks in the half-court, couldn't slow the Thunder down -- but it wasn't for lack of effort or execution. It was a lack of talent.