> If it had been legal, pure, and known quality that likely wouldn't have happened (he could still have been affected by addiction like our mother with alcohol, but he wouldn't be dead).

Overdoses on opiates happen even with legal opiates [1] and it's related to tolerance mechanisms. You become tolerant to euphoric effects much faster than you become tolerant to respiratory depression and nausea.

This basically makes opiates much more dangerous than any other drug class.

[1] https://www.cdc.gov/drugoverdose/featured-topics/overdose-de... - prescription opioids alone contribute to 9.2% of overdose deaths excluding alcohol.