The biggest rigging of American Idol actually became apparent in the second year but nobody cares. Aiken and Ruben both were in the studio recording albums before the show even finished. Everybody that goes to Hollywood gets a contract with a heavy studio option. If they’re popular enough in the voting that the record company they’ll be profitable they’ll make records no matter how they finish in Idol. Remember it’s a show made by the record company to make the process of finding talent profitable.
It isn't just about "finding" talent, it is also about marketing several singers for a whole season. They don't "suddenly" become famous when the season is over, they've already been test marketed for months.