Of course, I guess I should mention the late, great, David Bowie, who changed his stage personality and musical styles so many times it’s hard to count them all. Did the changes improve his career? How does one improve on perfection?
An artist who flipped for the worse was Annabella Lwin, former lead singer of Bow Wow Wow. She went for Brit-pop singles on her first solo album, and it was a near-total fail (except perhaps for the cover of "Fever"). This former Malcolm McLaren product’s career mostly vanished after that one solo effort.
Adam Ant also went from British New Wave/punk to pop, with mixed results. He disappointed his original fans, and made new ones in the Brit-pop world.
Spandau Ballet went from New Romantic to pop. They sold more records as a pop act, but many fans like me missed the edginess of their New Romantic sound.
One of the more dramatic shifts was that of Colleen Ann Fitzpatrick of Eve’s Plum, a power-pop/punk act in the early 1990s, who resurfaced as Vitamin C. Again, while a commercial success, she abandoned her original fan base.