Every team has beaten a team they shouldn’t. Didn’t the Knicks snap their long losing streak against the suddenly white hot Spurs?
To quote Bill Parcells, “you are what your record says your are”. In the case of the Mavs, they are 16-games UNDER .500 and the 2nd worst team in the West, 6th worst overall.
It’s factual to say that they’re not a good team. But that doesn’t mean they’re incapable of pulling off an occasional upset. However considering that Dallas is 7-30 on the road, that win over a struggling GSW was the rare exception, not the rule. That one game doesn’t supercede 45 losses and counting with 30 on the road.