They came in too light, it was like Black Hawk Down kind of situation. The DEA provided intel and the Marines made a run at him, but they couldn't pull it off. In Culiacan, there are punteros (lookouts) everywhere, all the cities outside too, any large movement of military personnel into the city is called in. There are military there, but the normal amount, it is an uneasy peace, and cat and mouse. if you bring in a convoy, the target will disappear into the mountains 3 hours before they get there. When they went for Chapo the first time, they flew in helicopters at night, and still they were alerted to the presence, and Chapo was able to escape.
The SEMAR/Navy is considered largely uncorrupted, which is why that is often the only group DEA will work with. I posted the video in another thread where they sent Blackhawks with mounted .50 cals and basically executed another boss in a different city, when he was running, and shooting it out with the authorities.