Mouseferatu
Hero
The claims come a combination of my personal experiences as a player of 20 years (specifically about what people were playing back then and still play today) and everything I have read about the subject. Feel free to research it, perhaps I could be wrong. However pricing of 2nd edition Dark Sun material on Amazon shows me that there isn't a lot of love out there for the setting, most of the products are priced like junk, a penny, 44 cents, etc. Only the main boxed set commands any sort of collectible price.
I'm afraid you're incorrect on several levels.
1) While DS was never as huge as, say, FR or the like, it was one of the more popular of TSR's "second tier" settings.
2) The fall of TSR cannot be attributed to Dark Sun, or to any single setting line. Rather, it can be attributed to--among many bad management decisions--the continued support of so many game lines, and the fact that profits from successful lines were used to prop up failing lines.
I mean, do you really think WotC would rerelease a setting that had failed? They do have access to TSR's sales figures, after all.