We call the past settled partly because it can no longer interrupt us in person.

Part of why the past feels finished is that it cannot answer back. The people in it cannot object to how they are described, revise their reasons, or point out what has been left out, so their story stays where we put it. Settledness is a property of our access to them rather than of the events themselves.

Hold your conclusions about the past a little more loosely than the silence invites. And notice the same effect with people who are simply not in the room, whose version is unavailable and therefore easy to overwrite. Absence is not agreement.