The director Denis [Villeneuve] is actually an actor (he's from Sons of Anarchy and he's a great character actor) and he's also a screenwriter (he wrote What Lies Beneath). It blows my mind to see when people from one sector move to another and excel. I think Sicario was one of the best directed and written films. It did get [a nomination for best] cinematography, though.
Detectives are only human; we're not Gods that know everything. When detectives tell their theory, in reality, most are rather anxious. Thinking that there's always possibility that they could have missed something, somewhere. . . But in return, the excitement you experience when your theory's smack bang correct is twice as great!