It may also be relevant that: if a group of five people agrees on something, then any individual group member need not agree. A member may keep their disagreement to themselves.
But if someone speaks at length about why this is the right decision, they’re more committed than “I’m willing to passively go along with this”. It’s a minor form of how a Mafioso is required to have carried out a hit.
Suppose the invasion of Mallorca goes badly. Do you want a merchant, a general, an aristocrat and a bishop to be able to say “that was a bad idea all along, those with power are unfit to wield it”?