Quite a lot of singers gained prominence through YouTube.
Justin Bieber, one of the most popular of the bunch came into limelight through YouTube, infact he is undoubtedly the most famous singer to gain prominence through YouTube.
Charlie Puth, The Weekend, Pentatonix, Ed Sheeran, Shawn Mendes, Carly Rae Jepsen, James Bay, Alessia Cara, Tori Kelly are few other singers that gained prominence through YouTube.
Many more are still on the rise and in no time they will because popular like these singers listed above.