Thing is, her original ass really wasn't that huge. She just came up during a time when the pancake ass was in. So everybody thought her ass was sooooo huge. I think I remember watching the original E true hollywood story on Kim back in the day and they said one of the reasons Kim stood out so much when she first started appearing was Paris was how different she looked from everybody. At the time, Paris, Nicole Richie & Co were basically walking hangers they were so stick thin. Same with a lot of the Hills girls that everybody was obsessed with in the early 2000s. As were the starlets from the OC, for example.
So when Kim showed up with her dark hair, dark complexion, and all her curves, she stood out even more and her ass became her thing. Same with Beyonce, and around the same time. Everybody was obsessed with her ass as well. Except Beyonce had more than her figure to back her up -- obviously. Kim only had the sex-symbol status to get her career going.