It’s a good theory, but not true. SpouseAnon works Homicide unit in So Cal. ( not very close to border) probably 8 out of 10 killings are grow related. The cartels are not giving up their income. They are taking out the little guys infringing on their money source.
Stats are kept, but you won’t find any of this in the news. If people knew how dangerous legalizing it has been, the state would lose a lot of Its tax revenue.