To the best of my recollection, Robin Williams is probably the most recognized celebrity to commit suicide since Marilyn Monroe. And given her career was so short, he was probably even more recognized. This alone is going to generate a huge amount of public interest compared to other celebrity deaths. On top of that, Williams was known for making people laugh. It's one thing for a brooding, seething, angry Kurt Cobain to kill himself but not Robin Williams.
But, yes, they could have even gone as far as to say he hung himself and leave it at that. This would've at least squelched the conspiracy theorists before they go off that he was murdered and something was being covered up had fewer facts been revealed.
They could've stopped there. We don't need to know anything else. But we will. I'm sure the toxicology reports will be released.