I think that we should break down your thesis into two parts:

1. Those acts preceded by a reason, i.e., the acts are informed by a rationale. The acts are rational to those actors, no matter how irrational they seem to us.

2. Those acts justified in the breach by a rationale. Those are irrational acts.

History has both, of course, but it's the second one that we should fear, because it's unknowable and unpredictable. The first one we can try to predict by understanding an actor's milieu.