Nail in the coffin. Glad they're getting out of the sinking ship.
They were having tons of issues with the mod team at /r/minecraft even months before any of this shit went down, with selective rule enforcement, overzealous removal, and preemptive bans happening if you ever questioned any of the modes behavior. Mojang's community managers were aware of those issues but were not able to do anything about it. I'd guess this is an excuse to decouple from that absolute train wreck.
Not sure about the third one, but those first two issues were resolved by massive revisions to the sub's rules (voted upon by the community) in December. Now instead of mods determining what they think the quality of the content is, they have a bot that allows users to vote on it instead.