What makes an event in History important?

Generally speaking, historical events of importance are ones that change the current situation, either: economically (economic crash such as 1929 Wall Street Crash = regression in development?/how large is level of threat?), physically (death of a King = who inherits throne?/potential instability in interim?) or any other means. Therefore, an event is important in general if it served to cause a moment of progression or regression/downfall in all sections of life, for example in: society, religion, or in the environment. Though, any historical event can be made important if you can manipulate/fit the evidence you give to say so. For example you might have lots of statistics on military failures, instead of figures on international relations as to why Germany lost WW2 - meaning you can argue this factor/the events in it as the most important.