> the Core Team placing themselves unaccountable to anyone but themselves
> we have been unable to enforce the Rust Code of Conduct to the standards the community expects of us and to the standards we hold ourselves to
It's possible that there were CoC violations that they were not able to moderate, that the actions available to them were limited (e.g., they would have initiated a ban but they were not able to ban a core team member), that a core team member intervened to prevent effective moderation, or that the core team prevented the mod team from being able to access official core team channels in order to moderate.
Seems to be a wide variety of possibilities and leaving the nature of the situation ambiguous* will likely make it difficult for a new mod team. I hope the now-former mod team are open and direct with new or potential mod team members about the environment they're entering.
* I do think it's right for the mod team to not reveal the specifics in public; that would likely provoke targeted harassment and make the situation much worse