I.suppose it could be one of those other party's you mention, but the US has the most motive IMO, Chapo's money, and I bet, the kids have some kind of evidence, that's working like a get out of jail free card...JMO
It's more of a military tactic than something Mencho came up with. The one thing all cartels have in common, their top mercenaries all received similar strategic training and as the US military experienced in the Middle East, urban warfare is now the dominant strategy.
Do terrorists/DTO have a better chance of survival in a big populated city or in the outskirts isolated from civilization?
I suppose it all depends, in the region and with these new rules of combat. Inside the city seems to be the safest spot.