Short answers, pulled from the story.
The Seattle SuperSonics officially relocated to Oklahoma City on the 2nd of July 2008, following a settlement between the team's ownership group and the city of Seattle. The team began play as the Oklahoma City Thunder in the 2008-09 NBA season.
The Professional Basketball Club LLC paid $45 million immediately to break the lease. The settlement also required PBC to pay an additional $30 million if Seattle had no replacement NBA team within five years.
Howard Schultz, then CEO of Starbucks, sold the SuperSonics to Clay Bennett's Oklahoma City-based group for $350 million. NBA owners approved the sale on the 24th of October 2006.
Schultz sold the SuperSonics after failing to secure $220 million in public funding to expand KeyArena, which was the NBA's smallest venue at 17,072 seats. The team had also suffered heavy financial losses during his ownership. In 2019, Schultz called the sale one of the biggest regrets of his professional life.
Under the settlement agreement, all items associated with the SuperSonics' Seattle history, including trophies, banners, and retired jerseys, remained in Seattle and were placed in the Museum of History and Industry. Ordinary equipment was shipped to Oklahoma City after the Seattle Storm completed the 2008 WNBA season.
NBA owners voted 28-2 to approve the potential move on the 18th of April 2008. Mark Cuban of the Dallas Mavericks and Paul Allen of the Portland Trail Blazers cast the two dissenting votes.