I am not so sure Ziggy ended up physically dead--just artistically dead. He went too far too fast and "the kids"--his fickle fans--moved on and outgrew him. They figuratively "killed the man" and broke up the band.
Why do I think Ziggy didn't really die? Because, in Rock 'n Roll Suicide I see an older, aging Ziggy crying out to the young rock gods du jour "I've had my share, so I'll help you with the pain, your not alone, gimme your hands." He also speaks of walking by a cafe "but you can't eat when you've lived too long." So Ziggy is older . . . not actually old, but deemed "old" in the ever youth-obcessed world of popular music. His fans have moved on, Ziggy is washed up, but he still recalls both his glory days and the agony of stardom, so he reaches out to the new clueless rockers of the day to help them through the pain.