The artists you mention had so much more to give us all, as you say, and it is our great loss, for not being able to witness it.
Felt the same at the premature death of one of my favourite childhood film star icons, Steve McQueen, who sadly died aged 50, to cancer, after a short two film comeback....which he was very ill during filming.
McQueen believed that asbestos used in movie sound stage insulation and race-drivers' protective suits and helmets could have been involved, but he thought it more likely that his illness was a direct result of massive exposure,while removing asbestos lagging from pipes aboard a ship while in the Marines. Sad.