You're looking at this as if Dame is just an employee and he should be willing to take a reduced salary so that his employer can put other better employees around him to achieve more success.
In my somewhat strained analogy, Dame is a business (Porsche in this case). He has his music career, he has his endorsement deals, and he has his basketball talents all available to market for his best financial advantage. The Blazers are where he has currently contracted to use his basketball skills. Once that contract is up, he's entitled to sell his basketball talents to any other team, but the Blazers want to, in essence, continue to drive the Porsche. They also want to have other pieces around the Porsche to make the most impact for their own marketing ambitions. They operate in a business environment where the top-end talent is necessary to have any success. Expecting that you get the Porsche for less than market value just so you can buy lesser pieces is not a realistic business plan.