They figured Chris would talk if put under pressure so he became expendable when the mission went sideways.
If you saw the Movie, "Shooter" it's just like that. Once the clandestine mission is compromised, close up shop, deny any involvement and let those on the front line fend for themselves and/or die.
You've got to remember, these pukes making the decisions don't think like Patriots. They would never think that someone would come to the aid of the Ambassador or others in that compound, because if it were them they would have been on a plane after the first round was fired. Hitlary and Kennedy both know of security risks that is why Hitlary had a forward team come in before her visit in that part of the word.
Clancy's Clear and Present Danger, too.