The only problem with your theory and long rant, Jazzfan, is that a Deron trade had been floated earlier in the season. That doesn't sound like an owner or GM who wants to blindly follow their superstar.
The problems with Deron may have played a part in Sloan leaving, but I don't think it was the entire reason. I think Sloan just grew tired of multiple players not running the offense, of the poor defensive effort most every night. The fun was gone. Great players inexplicably walk away: Barry Sanders in the NFL, Karl Malone when he was in sight of the all-time scoring record. And Sloan when he just had 2+ seasons to go before becoming the all-time winningest coach. Don't forget, he got the job when another pretty good coach just decided he had finally had enough.