treatable mental illness (i.e. if he would just have talked to us)

It's not that simple. Sometimes the illness is perfectly treatable, but in practice you're never able to get treatment before you die, unless one of the people you talk to goes far beyond the call of duty and drops their whole life to help you get treatment and magically divines how and when to help instead of behaving like a bull in a china shop and making everyone else terrified of mentioning depression.