I'm very aware of just how horrifically violent cartels can be. I'm not ignoring that or condoning their behavior.

Historically, there have been many instances of powerful groups of people willing to commit atrocities to stay in power. In some cases, it's still useful to attempt to negotiate or explore peaceful solutions. When you're negotiating, it's often useful to look for some kind of mutually beneficial outcome where both parties get something valuable, while giving up something less valuable. I have no idea if this would actually be possible in the case of drug cartels, but I think it's worth considering.