Wasn't Dark Sun written as Brom's work arrived across the TSR desks? I feel like I read that they built a setting around his art. 4e probably had the benefit of being developed with plenty of lead time and around solid rules.
Here is a direct quote from Brom:
"I pretty much designed the look and feel of the Dark Sun campaign. I was doing paintings before they were even writing about the setting. I'd do a painting or a sketch, and the designers wrote those characters and ideas into the story. I was very involved in the development process. I've been fortunate to be involved in the development end of a lot of projects I've worked on, from role-playing games to computer games."