The unknown reason is "talent". Fantasia is Great, with a capital "G".
Diana has the potential for greatness, but she's not there, yet. She'll for sure get recording contracts and I'll be applauding for her, but she's not better than Fantasia.
Sorry, the most recent black girl who was eliminated had more talent in her little finger than Fantasia. Her voice was more pure and versatile.
I guess it's subjective. Fantasia screeches in my ears. LaToya was the real talent. Like Clay, I would buy her cd without being the winner. Of the remaining two, I might buy Diana's cd, but no way Fantasia's. She's got a big following though. Hey, the judges will all buy her cd if no one else.