He had a severe benzo addiction and rather than going through the normal treatment of tapering off use, he opted for an experimental treatment offered in Russia where he was instead placed in a medically induced coma to avoid the worst of the withdrawals. This had other side effects though and he later described having to relearn basic motor functions after being awoken, so who knows what else that did to him.
You might think that but it’s actually established parlance
https://en.m.wikipedia.org/wiki/Incompatible_with_life