Since shit has been hitting the fan for the common people there's a fundementalist movement in that relgion they have. Makes sense, and you see alot of parallels in real life.

Cersei's dumbass decides to effectively give them assets and legitimizes them to de-stabalize the throne since she's got no more real juice there with Margery as Queen. Its why she sold out Loras and told them he was gay, so they could arrest him.

The problem is that if they have so much juice they can openly defy the king...its gonna be a headache in the future.

Notice how when she met the cousin she was fucking where they first introduced this storyline he was fully converted and not listening to naan she had to say...she's not going to be able to control them and she's effectively put in ANOTHER player you gotta deal with for the fucking throne.