Once again then, focussing on what matters - Vivian Campbell left DIO (the band named after namesake Ronnie James Dio) because he thought the band was going in the wrong musical direction. At that time, he was considered the new Randy Rhoads.

There are many reasons why people leave bands. Health is one of them. Stop judging and comparing without having a clue what you are talking about. Especially giving Vivian Campbell as an example, when he's always been a mercenary. But what do you guys know?