The majority of people who make it have something extra. Not necessarily talent, but some nuance in their character which pushes them earlier, and further into public conciousness. To be successful in the entertainment business, you have to push, push, push. They don't care how they have to get there, or who they have to cross to reach the peak. Their main objective is to get there, and they'll do everything in their power to achieve that.
Exploitation plays a very large part in that.
The casting couch can come into play. Many stars have to sleep their way to the top. Male and female. The very straight Clark Gable had to demean himself by sleeping with male casting directors, just so he could have a chance to audition. That's more common than you'd think.