I think it was a combination of factors, most of which have already been mentioned before me:
- Kris is non-threatening pop compared to Adam's wild vocals and artistry;
- Kris is cuter to all the 8-14 year old girls who have cell phones and KNOW how to use them;
- Adam is gay, and you can say that shouldn't matter, but it still does;
- There was backlash because of the judges' perceived push for Adam to be the winner - sometimes people don't like being pushed.
- Kris picked up Danny fans because Kris is much more like Danny than Adam is.
- (Edit) I have to admit that I agree with the person above me is right, that Kris was a little better Tuesday night, the one and only night I believe the case could be made that he was even in the neighborhood of better. Adam seemed uncharacteristically nervous or something, and was not at the top of his game.
I feel sure it was not any one thing. However, you can chalk me up as a disappointed fan because my boy, Adam, lost last night.