The celebrity flameout is a Hollywood cliché — a mantel worn tragically by the likes of Lenny Bruce and John Belushi and handed down through the years to tabloid-populating stars such as Lindsay Lohan and Britney Spears. But Michael Jackson, dead at 50 after a life marked by unrivaled heights of pop brilliance and bizarre behavior that threatened to overshadow it, stood at the pinnacle of celebrity and embodied all the turmoil it can entail. It’s a perch experts say played a major role in his troubles in life and, perhaps, his untimely death