Robin had a lot of demons but packed a lot of life and love into his years, as well. I am quite sure his death is a lot less sad than how most people choose to live (or worse, are forced to live). I am not a big fan of suicide but approve of it in certain situations. If I develop Alzheimer's, grandpa is going to see if a few friends will make good on their promise or start heading northbound on the train tracks until I see the big white light or test my jump instructor's theory that you can land from any height safely from any height without a parachute if you just execute your landing fall perfectly.
He was really into conspiracies, so much so that he would get incredibly depressed unraveling the atrocities that are being hidden from public eye. I don't think it would be far out of the picture to think an obsession with something that has no tangible benefit to a practical life would lead to crippling depression as he tries to carry the weight of the worlds tragedies in his cranium. Or he found an atrocity so bad he had to be silenced for it (a la Michael Hastings). But cocaine is a hell of a drug, sad he's gone, but he has a lot to show for his life, and certainly made positive impact on many. May his afterlife journey be full of wonder.
a drug addict commits suicide. it doesn't really have to be more complicated than that. also, suicides go to hell. his afterlife journey is gonna suck.