Does Europe produce one would-be conqueror per century?

Why does Europe seem to produce one would-be conqueror in every century?

It is not really once per century; most centuries have several expansive rulers, although only one or two make a serious attempt at much wider conquest.

Napoleon, Hitler, and Putin are offered as examples of a European would-be conqueror appearing once every century. The proposed frequency is too tidy. Frederick the Great provides another example, and most centuries contain two or three rulers with ambitions for much wider conquest. Usually only one or two make a serious attempt, so the apparent sequence reflects selective memory more than a regular historical cycle.