As someone said recently, AI masquerades as a singing contest, but it's really a "who can get votes" contest. Every year there seems to be a person on the show who seems to get much further than they deserve, because they seem to get some strange bloc of voters and that carries them. Last year it was the goofy looking kid, Kevin, the year before it was the fat bastard, Scott, and this year it is the kid with the good hair, Sanjaya.
Stephanie was not the 11th best singer remaining, but she got caught in a voting squeeze between 2+ other black chicks (I'm not quite sure what Jordin is), one girl who's willing to flash a little skin, and a rocker chick who is being kept around for the novelty of it. She simply didn't stand out.