A watched pot will boil.
As it heats up, there’s no way to predict where the cavitation will start and which bubble will arrive first. But with enough time and enough heat, it’s going to boil.
That tree down the street is going to lose its leaves this winter. We don’t know which leaf will go last, but we can be pretty sure they’ll go sooner or later.
Complex systems can be predictable even when any individual node in the system seems unknowable.
One of the traps that marketing measurement presents is our unwillingness to consider populations instead of individuals.