Why not try the whole council of war?

Could war by committee have been followed by a trial of the committee?

Collective decisions also exposed several patrons to blame, giving them a shared incentive to protect the officers they had promoted.

Trying the whole council would spread political exposure to the patrons who had promoted its members. The suggested mechanism is that each patron had an interest in preventing responsibility from being isolated or extended to the group. Collective decision-making therefore gave the officers a measure of political protection after failure. This is an explanation of incentives surrounding accountability, rather than a formal legal rule barring prosecution.