The largest cartel in Mexico was created by former US agents funded by the US. The government isn't as competent as you think it is. It's incredibly difficult to reel in an entire network with massive proportions.

Now add to the mix if, God forbid they figure out who you are, who your children, wife's family are. If you get a pic of your niece with a clear threat "stop or we will murder her" you bet your sweet ass you're going to rethink that plan you have to topple the cartel. If you don't listen, they murder her. Then you get another pic of your wife....