. . . However, the things that Cozumel are saying is pretty much the same thing that the Cancun (and Mexico as a whole) folks are saying. Why would the state department choose to believe one and not the other?
Because the State Dept. is a vast bureaucracy that is continuously churning out reports, some of which bubble up from the underlings far enough to finally get someone to approve turning them into Travel Warnings, while others are still in the process of being written, approved, sent on up to the next level for further approval, etc.?