Well there's two things that crossed my mind when I started reading into this thread: One, there's folks over there that wanted to show Trump just how ridiculously asinine he is from claiming they'd pay for His Wall. Secondly, the Mexican politicos needed a convenient scapegoat to sidestep their own inability toward not being corrupted by all that drug money pouring into their country, infusing their economy with $$billions$$ of yankee dineros on an annual basis.
It just makes logical sense that if they have drug lords over there being able to arm themselves to the hilt no problemo impunity and immunity-wise, then they're (Mexican powers that be) either in cahoots with the drug dealers like way up the chain, not able to/not wanting to control their drug dealing problem the way they should or more than likely both.