If the manufacturers and regulators were more concerned with human lives than making money, they would have quietly buried the research. It may have entered the illegal market eventually, but there wouldn't be factories producing large quantities of the drug like there are now.
They should have known that an opioid 50 times more potent, deadlier, and more addictive than heroin would be responsible for the worst drug epidemic the world has ever seen.
I think we fundamentally disagree here. There might be some 20:20 hindsight way to completely avoid the opioid crisis (especially with the behavior of Purdue Pharma), but from my perspective if Fentanyl (or other potent synthetic opioid) reaches illicit manufacturing it almost always becomes a dominate force in the black market. The cost, strength, and ease of smuggling are big perks. Regulators have little impact on what black market drug labs produce.
They should have known that an opioid 50 times more potent, deadlier, and more addictive than heroin would be responsible for the worst drug epidemic the world has ever seen.