Ashanti is a classic case of being a filler artist, Aaliyah had died and Brandy was pregnant... Beyonc? had not become a solo star yet and for that summer of 2002 Ashanti filled the perfect gap and used to that to her advantage, once real compition came, she would fade into obscurity again.
I believe they gave Lil Mama a lot of big features and opportunities simply because there were no other female rappers, I do however think she is talented, but for some reason, she could never get it back and nowadays
Trey Songz only slayed when Chris Brown was tumbling and a new gap opened for him to shine. If he was truly capable and talented in his own right, he'd be a superstar in his own right by now.
The Austin Mahone girl only gained steam when Justin was in trouble for stuff.