Why/how are the cartels not just "put down" immediately with some assistance? Is there something deeper, like people being born into it or politicians much rather having drug money than a living population? I don't understand why there even needs to be any form of civil war, unless the cartels have embedded themselves deep enough to be similar to guerilla warfare-esque with innocent actors.
Take a cop in rural Mexico making like $15k/year, and he'd be absolutely insane to flush his and his family's life down the toilet to go up against these guys.
Cop in the US in one of those militarized police forces is making upwards of $70k, and isn't up against organized groups of psychopaths with armored vehicles and automatic weapons. Those cops are going after guys growing pot in the closet, and the occasional small, low-level drug org that isn't too dangerous.
I don't know if that would start the process of gradual downsizing and elimination by security forces or if it'd instead first lead to a huge uptick in violence and perhaps civil war, but I feel like in the long-term it'd be much harder for most of them to hold onto as much money and power as they used to.
I'm absolutely not an expert in this area and could be horribly wrong, but I think this idea should at least be considered more seriously.