I have a theory that all of those singing contest shows on TV are connected to the Witness Protection Program, because most of those people are never heard from again... even some of the winners. "He's singing on stage tonight and he'll be singing in front of a jury next week..."
Somehow it is both a fast lane to fame and a fast lane to obscurity. Again, kind of like testifying against the mafia. After the people walk off stage I picture them being hustled into a van by US Marshals. "Great song. Once we land in Nebraska you will officially be known as Pam Smith and start work in a store that sells only cat toys."
Being promoted by a major TV network can be good for racking up a large following quickly. But that does not seem to help you keep a following, especially when next season the network not only abandons you, but also puts its weight behind a whole new crop of singers.
It's not about the followers who appear only to disappear. It is about the followers who stay with you.