I wanted to like the scene with the preacher but I can't remember from last night what actually put him over the edge. Just wasn't his character to do that. Because of Saddik? Because he took away the doctor and his girlfriend has an infant? All the things he's been through with Negan, etc., and he chose that guy, who was in no position to do any more harm, to go nuts on? IDK, guess I just didn't buy it.
IIRC, Carol's character in the comics is dead at this point (not a spoiler). These writers don't have any story arc for her to go by (from the comics) and they, it appears, just decided to make her a reckless, impulsive liability to the group. Well that's one way to go I suppose.