You need to understand Mexican history to appreciate this.
2000-2006 Libertarian leaning Club for Growth type Globalist Vicente Fox was President of Mexico. He let the cartels grow, unimpeded by Presidential action. The Mexican population was very unhappy with the drug policy of Fox and for that very reason swun to Calderon, a social conservative of the samee PAN political party, the party of devout Catholics and small businessmen, the survivors of the Marxist genocide supported by the Rockefeller Republicans in the US.
Calderon was president 2006-2012. He went after the cartels with a vengance 40,000 maybe 50,000 Mexicans were killed in gun battles 2006-2012.... not as many as in the Marxist genocide, but still a lot of people.
In 2012 the Mexican voters were sick of the drug wars. That is what they voted for in 2006, but not what they expected. So they returned to the PRI party, the party of the cartels, the party of corruption, a party very much like Chicago Democrats. It turned out the PRI president was totally incompetent.
In 2018 all the parties of the past were split. The PAN party split along both personality and ideology issues. The PRI party split also. The third party, the PRD which had naver been given a chance at president also split. The hard left ideological wing of the party went one way. The populist wing of the PRD went with their populist Governor Obrador and won the Mexican Presidency in a very split decision.
So now there are not just a Mexican Hillary and Romney factions, there are 10, maybe 15 different factions, none of whom like Obrador, nor each other.
Mexico is different than the US. In the US the military does not get involved in law enforcement. In Mexico there is a long tradition of the military getting involved in law enforcement and local affairs.
That is the back story for this alleged story.
How did all those weapons get into the hands of the cartels?
Has Eric Holder been retained as their purchasing agent for high-powered fire arms?