I'm not convinced that removing Monica as a moderator was a mistake.
She made it clear in a comment quoted by The Register that she refused to use the singular they in any circumstance, even when it was known that it was someone's preferred pronoun.
And in the leaked transcripts (if you trust them) it seems she was repeatedly asked to rethink her stance on this by other moderators, and repeatedly refused.
Obviously SO could have done a better job in terms of the process, timing, and communication (which is what they apologised for), but ultimately it seems that she's just not not a good fit for SO. There's no suggestion that SO is not going to enforce a rule requiring moderators to use people's preferred pronouns, when known and when appropriate, and Monica was very clear that in at least some cases she would not do so. So...one way or another, she was clearly going to be removed, right?
Arguably she could be re-instated today and then re-removed later in the week when the CoC changes come into force, but to what end? That doesn't help her, SO, or the community. (And that assumes she didn't violate the existing CoC, which is still disputed.)