Washington State has no state income tax. California has a marginal state income tax rate of over 13% for high income earners. Well duh, of course the Kings will move to Seattle.
If you go back and review how the Sonics left...no one in the city government cared to launch a new arena. They were playing in a place that needed massive renovation...which wasn’t going to occur, and the city felt that they weren’t drawing any tax revenue or money for town.
After the Sonics left, then the town realized that they had screwed up and there was a base of income related to basketball.
Professional athletes are taxed depending on which state each game is played in; ie what percentage of their income was generated by each game. They pay A LOT of states every year. So, with the high income players, this will have minimal impact on CA tax receipts. The support staff, on the other hand (coaches, trainers, etc) almost always reside where the team calls home and pays taxes accordingly.