That could be a Mafia gambit that failed due to unforeseen circumstances - for example, Teruteru and Leon being default executed. Even if that wasn't the game, it was clear even from Day Two that Byakuya was clearly agitated at the state of the game. Maybe he deliberately invoked a risky strategy in order to leave the game early which ended up paying off for the Ultimate Despair.

There is one avenue I do not think we have discussed - is it possible for either Nagito or Chiaki to be a Despair-aligned power role? Sir Monokuma said in the opening post that roles are not aligned with any particular faction. While the notion of a Despair-aligned Doctor seems peculiar, to say the least, a Despair-aligned Cop seems plausible. If you take into account the number of power roles that are dotted around the student population, a Despair-Cop would have utility in identifying Town power roles in order to neutralise or kill.

I certainly think it is a possibility, and now that Chiaki is continuing to be conveniently role-blocked, thus providing us with solid information other than the claims she has put forward. And a Despair-Cop would do well to align themselves with the student Doctor, presenting theories that are backed up both from investigations and also knowledge of who is Despair and who have eyes full of hope.

For the record I still think Nekomaru is likely a member of Ultimate Despair, but I can't discount there being another role-related twist.