Oh so this just makes perfect sense..

I wasn't even considering the occult symbols and mythos down there that could be used to further a cartel's purposes.

The exorcisms and prayers would work as a level of social crowd control too. Driving out the "evil spirits" that are controlling the cartel. It gives the people a narrative that emboldens hope, rather than defeatism in spite of the circumstances of their environment.

The Cartel consists of people possessed by the devil, but god is on our side, so don't give up just yet