The theory goes that the Mexican government decided to "pick a winner," and it chose the Sinaloa Cartel. The small number of arrests and seizures of Sinaloans, compared with the other cartels, strongly supports that theory. The much-trumpeted capture of Chapo Guzman argues against it, but not if the fix was in for Chapo to depart after little more than year.
The Sinaloans -- again, quite possibly with the help of the government -- have emerged victorious in the cartel wars, and a relative peace has settled onto Mexico after the hideous violence that took at least 100,000 lives.
The Mexican government is understandably desperate to preserve this "Pax Narcotica Sinaloa," but drug-related killings are on the rise again in Tijuana, and a violent, relatively young organization, the New Generation Jalisco Cartel, is challenging for power. It's possible that Chapo Guzman, with his influence and prestige, is more useful to the government on the outside than behind bars.