There are people who were born with a singing proclivity and they have enlarged vocal apparatus which is suitable for opera. This is generally shown at an early age.
The rest is perspicacity combined with a drive to do this.

The raison d'etre of a good vocal coach is to help the student save his/her voice from deteriorating by the use of sound vocal technique.

Abuse of the vocal folds is common among performers who belt and strain in their styles. Unfortunately, some of this spills over into folkie territory.

We know aging performers who have lost their voices due to abuse.