I wrote in this thread (or it's equivalent) after the Finals last season that the Mavs were a one-off champion and that Nowitski, after waiting 13 years or so would be one and done. And just like nearly all of his other seasons in the league, this one ends with his failure to lead his team to the next level or, in this case, an even competitive level.
Last season Dirk was considered the "Golden Child" of the NBA but in reality he was no different than he was this season. He got his points just as he has in past seasons, only this time, as usual, other than last season, his teammates failed to pick up the slack.
Marc Cuban has to take some of the heat too for the team's failure this season. He allowed two important parts of his team's core to walk in free agency -- Barea and Chandler -- because he didn't want to pay them. That is a huge no-no if you want to win two in a row. Speculation is that he did it to free up cap space in order to sign Dwight and/or Deron Williams, well he may not get either. In the NBA, you don't set your sights on "pie in the sky by and by", that "pie" may not ever come. The league changes fast.
So Dallas becomes one of the few defending champs, if not the only, to be swept in the first round of the playoffs. How embarrassing, especially to a team who was so obsessed with their one championship that their fans complained loudly when they felt the Lakers P.A announcer didn't refer to them enough times as the "World Champion" Dallas Mavericks.
But, the truth is they probably aren't that bothered at all. after all, they got their championship so what other worlds are left for them to conquer? Maybe it is only Lakers fans who consider "one" championship a "jumping off point" and not the final destination.