Why didn't Demi Lovato become as big as Miley Cyrus and Selena Gomez?

She's pretty famous, obviously, but her music and acting never took off the way that Miley and Selena's did.
I think her music is better than Miley and Selena's, yet she never sells as much records or gets as much streams.
So, why didn't she become as famous and successful as them?
2 answers 2