No, you don't get it.

It is the illegality. Bootleggers killed each other during Alochol Prohibition. Once Prohibition ended and the alchol trade became legal that stopped . . . Alcohol didn't change so it wasn't the alcohol that was causing the murders it was the fact that there was no legal system for sellers to resolve disputes and only those who were willing to violate the law were in the business.

The vast majority of the killings you refer to are business disputes not drug induced murders.

Look lets say you and I are both salesmen selling the same product. If I have a dispute with you I have legal recourse. If I think you broke into my house and stole my products so you could sell them I can use the criminal and civil legal system to seek redress.

If the product we both sell is marijuana, the legal system is not open to me. I mean I can't go to the Police and report that you stole my marijuana. I can't sue you for the value of my marijuana. The only way I can stop you from stealing my marijuana is to use force.