"BIG payoffs, or part of the collusion?"
Ummmm, how's about BIG payoffs AND part of the collusion?
That whole country runs on juice and kickbacks, it's been a way of life for hundreds of years, sad to say. We're talking bribery central and at least in the past it goes from the very top to the very bottom.
I did somebody a good turn years back and in return I had an offer of a free villa down there on the coast. They told me right up front that wifey's brother was chief of police [actually more like a county sheriff but I don't understand their system] so I'd be free to carry on life there any way I wanted, never a worry for the rest of my days. To make it clear, that would include smuggling, murder or any other crime I happened to commit! The Federales are on the take too.
My guess is extraordinary kickbacks in all directions. I recall there was an issue of an awful lot of money unaccounted for in some American agencie's budgets, large millions and billions. They were involved in this up to their hairlines.
Overall, there's not a whole lot of differene between the Mexican way of doing business and the various govt. offices stateside, it all runs on bribes, kickbacks, special favors, threats and extortion. For the various extortions we see the random expose' and unfortunate accidents as a word to the wise.