There is no overnight success in business and it is no different for the entertainment business. The reality is that majority of people that think an artist made it overnight is that they never paid them any attention nor cared until they made it big.
However, artists like Beyonce, Rihanna, Jay-Z, Chris Brown, etc. all started very young and dedicated their lives to the craft by practicing, performing, networking, and building their brand.
There is no overnight success! You just never paid attention to them before they made it