You may say, "How can someone who can't sing become famous for singing?" Easy... some people have a, "look," and a minimal amount of talent. They are known as studio artists. Singers who need the benefit of auto-tuning and correcting and mixing done by machines to make them sound like someone who can actually sing. Their voices are just raw material for the sound sculptors to work with. These are the artists who get caught lip-syncing a lot. Their music isn't bad... you just wouldn't want to hear it live and in person.