Why did Sophie never end up as popular as Diana in the celebrity stakes? She's as beautiful, high profile, etc.
There was a huge amount of interest in who Charles married. But also Diana did have star quality. Sophie, with the best will in the world, didn't.
She looked a lot like Diana but in a diluted way. She didn't have Diana's way with the media. We thought (mistakenly) that Diana was shy, but in fact she was artfully coy. She had a twinkle in her eye that was very winning.
Sophie has turned out to be a rock solid royal, but she didn't have the same appeal as Diana. And probably no bad thing.