Ruben won because the judges kept telling the audience that he was the best thing since sliced bread. In the meantime, they -- especially Simon -- often managed to find ways to downgrade Clay's performances.
At one point, Simon did a great disservice to young people all over the country when he said Clay was "too Broadway," or something to that effect. Simon meant it as an insult, as though being able to do Broadway musicals is a bad thing. The kids over on the AI boards still repeat that as a way to insult contestants they don't like.
I remember when they were down to the final four or so, the audience suddenly (and almost unanimously) became pro-Ruben. Curious.
I don't know if we'll be seeing Clay returning on AI any more ... apparently he successfully got out of the 19 contract. Last time he was on (when he sang Earth Wind & Fire's "Fantasy", which I really enjoyed), Simon and Randy made fun of him on some morning show the next morning. It was just classless. So, who's selling out shows everywhere he goes? Not Simon and Randy. I'm very pleased that Clay was able to escape the planetary gravity of the AI machine.