Supply and demand
During the era of the Raj, India was the leading poppy grower. It was sold worldwide as a treatment for hysteria in women and hyperactivity in children. Only China refused to have anything to do with it because it was addictive, but two opium wars taught them how to take it.
By the early 20th century, however, it was clear that it did more harm than good and was withdrawn for the most part. Too late because it was found to aid sleep, lower inhibitions, induce euphoria. Demand increased. Other drugs with similar effects were introduced.
It seemed worth breaking the law to obtain it. A situation similar to the days of prohibition arose. Criminals caught on quickly. Give the people what they want, at a profit. The gangsters of today merged with the bootleggers of yesteryear.
The Golden Triangle and the Middle East largely focused on Europe, Latin America largely on the US as growing and smuggling dope turned into a multi-billion-dollar business, more accurately cartels. Run not by drug lords but by warlords.
Brit author Ioan Grillo has made them his niche in literature. In Gangster Warlords, he interviews the respective warlords in and out of prison. He notes that whether from Mexico or El Salvador, Honduras or Jamaica, they have rags-to-riches backgrounds.
Their security guards are serial killers many times over. Twenty-five murders for each is average. Does it prey on their consciences? Are you kidding, Gringo? At times, government forces join in.
Now and again, the populace gets fed up and forms vigilante groups. Bloodshed, kidnapping and rape are common. Those governments not corrupt are unable to deal with the situation. Neither are international law enforcement agencies.
Is legalising drugs a feasible solution? When you come down to it, people are the problem. Tell them something is prohibited, they want it. Unfetter weed and they’ll clamour for the stronger drugs.