I'm a fan (and you should be too) because...
Well... I don't really know....
It could be because he's charasmatic and you're bound to like him eventually (I do that too! ).
It could be because I think he's really, really, really good-looking and I love him out of pure lust.
It could be because I liked his song choices, predictable and unpredictable at the same time.
It could be because I think he was the best singer there and that I knew he would win.
Or...
I could think all of these things (except for the second one; he's good-looking, but I could hate his singing too, but I don't). And I could be a GIANT fan of his!

That's why I'm a fan.