From what I remember, and most of this is from my uncle who was an avid Sonics fan, he was telling me the arena was "far too outdated" as claimed by the league and owners, and with Seattle's refusal to help fund a new arena, they had no choice but to look into relocation. There seem to be some theories around that it had to do with the ability to sell tickets in a newer building for higher prices, and also that there were not enough luxury boxes to sell around to the wealthy folk. Again, whether this is 100% true or not, I'm not sure. It's likely to be a bit of bitter exaggeration from the fans of the Sonics.
The biggest problem I have with the Maloofs, is their recent behavior when it comes to trust and their word. You can see glimmers of it in the last 24 hours. From a deal that was almost a certainty, to being up in the air again.
They came to an agreement on how to help fund a new arena here in Sacramento last year. They met with city council and sat in when the agreement was hashed out. They took part in negotiations (along with their team etc,) and they shook hands with Kevin Johnson in front of the press, crying, saying they've finally reached a deal. They went on to take the floor of a Kings game, and announce again that they had been so relieved to reach a deal, and that the Kings were staying in Sacramento! ...Then a few weeks later, they backed out, saying they didn't like the way the financials of the deal broke down.
We had to deal with a couple years of that, and all the while, ticket prices continued to raise while our team continued to be neglected to be improved. It's tough to see them treat the city that loved their team like this.
Hopefully it works out for everyone, and we can all be winners, but I'm very much prepared to be a Sonic's fan now. I even have an old Gary Payton jersey my uncle got me when I was a kid.