Writing for Americas Quarterly, professor & journalist Pérez Correa takes Mexican President Andrés Manuel López Obrador to task for utilizing the military for a wide variety of security and other tasks, after promising not to do so. The points she makes about the risks of militarizing society are real enough, as has beens shown repeatedly in various Latin American countries large and small.
On the other hand, presuming AMLO doesn't want to let the cartels take over Mexico completely, what other choices does he have? The police are either on cartel payrolls or too frightened to do much.
It's a country where the feasible alternatives are few, and presidents serve one 6 year term. A president gets elected, wants to do well for the country, looks around for meaningful ways to move things in a positive direction, and sees basically, the military and nothing else.