Crimson Desert used to launch, but now Steam returns to the Play button or the game briefly shows a black screen before closing. Verifying the game files, reinstalling the game, and trying several Proton versions did not help. What would you try next?
If those game-level steps have already failed, try reinstalling the Steam client itself. That fixed this particular launch problem, though it may not be the answer for every system.
The timing leaves the cause unclear, since both the operating system and the game changed around then. Still, after several Proton versions and a fresh game install made no difference, the Steam client is worth checking before spending more time cycling through the same options.
Answers are reviewed before they appear publicly.