I actually almost feel bad for Karl. He did a great job in Denver- 9 consecutive playoff appearances, 6 straight 50+ win (non-lockout) seasons, 57 wins in his last year (franchise record in the NBA). He succeeded with Carmelo, then did even better when Carmelo was gone. Yeah, he couldn't win in the playoffs, but he wasn't exactly coaching teams that anyone would pick to win titles. Denver management got greedy, couldn't see the forest for the trees, and started thinking that Karl, who was clearly a big factor in their success, was actually the one holding them back from challenging for titles. They pretty much forced Karl out, and I don't think he really wanted to leave, or wanted to be out of coaching for a year.
That said, Karl should have accepted what he was walking into in Sacramento, or not taken the job. You can't go to a new team and then try to use them to reassemble your old team (which seemed to be his goal in pushing for Cousins to be traded). And I'm predicting that this is going to end so badly that neither Karl or Cousins will be in Sacramento by the start of the 16-17 season. I think Karl will be axed during the upcoming year, then Boogie will be traded after the year.
