Breakdown of what Bruce said
A user has been getting in trouble a lot recently
Completely accurate.
so we've been trying to discuss him
Accurate as far as I can tell.
but it's going slowly.
Read "It's going slowly because I like dragging things out because of the SoM and I have made things hell so no one really wants to stand up to me"
Emprags banned him
True.
and I criticized the ban for several reasons
Several reasons, yes. Good reasons? Who knows.
His response was to unban the user, demod himself, and write posts announcing his departure.
Correct.
Answers to your questions.
What's the mod drama about?
The mod drama is mainly about how the sub is run, how the mod team functions (read as how it doesn't function), and built up anger. There is definitely more to it, but that's the gist of it. Lack of communication also is part of it.
Who are the major players?
Outsider, brucemo, the rest of the modteam, and some of the former modteam.
What did they do?
Outsider: He has allowed one moderator to single handedly drive away more mods than I have seen leave in all of the subreddits I moderate.
Brucemo: He has driven away several moderators. From multiple reports, he is basically impossible to work with. He makes it near impossible to ban users who are destroying the sub.
Rest of the modteam: Well, they really haven't done much. However, a lot of what they haven't done is of no fault of their own. Sure, they could all stand up to Bruce but, without outsider doing the same, it'll just create more problems and may get them kicked off. Who knows at this point.
Mods that have left because of Bruce: They have all left because of the crap that is going on in that team. They refused to take any more of it and so they left. Basically, why hold up a few bricks when the rest of the building is crumbling around you?
TL;DR: Many mods have left /r/Christianity's mod team because of brucemo and his shenanigans. The team is not a team and those mods didn't want to put up with it any longer. Nothing is going to change until brucemo leaves, is kicked, or (miraculously) changes his attitude.