You say: Their suffering was self-inflicted.
I reply: All suffering is self-inflicted.
I'm not talking about pain. Pain is daily. Everyone experiences pain. It's a signal that something needs attention, or that changes are needed. Toothache says "go to the dentist." Sadness says "notice what's going on, take care, use skillful means for healing."Some pain is so awful, some agonies so deep that they demand attention from the community. Famine, fire, and flood require fast responses. Buddhists have a good track record for relief of pain.
But suffering is different. I know nothing first-hand about Elvis, Michael, or Whitney, but if the stories of their years of drug abuse are so, I know they suffered.