No matter what, we have to believe we know why things happened. Some people believe in vast impersonal historical imperatives, others in sinister conspiracies, yet others in divine providence. 

A couple of months ago, Greg Cochrane, in his interesting and crabby blog West Hunter, brought up an example of the poverty of historical explanation: for a couple of decades after the Second World War, historians wrote accounts of what had happened in that war, and why, without any knowledge of a significant influence on how events turned out, the breaking of the Enigma codes. But no one (as far as I know) said "actually, the defeat of the Germans, and the US victory at Midway, and a whole bunch of other things, seem unbelievably lucky. Is there something we don't know about them? Were there, maybe, some spies who have not yet come to light? Or some other explanation?"

I do remember a good friend saying, after the publication of Winterbotham's The Ultra Secret, the first big public explanation of the breaking of the codes, and the effect that had on the war: "No one understood anything about it!"

Now, maybe, we do. Though the Soviet victory in that war, which really decided things, still makes no sense at all to me. No code breaking for them, no secret weapons, no across-the-ocean safe haven pumping out bombers and cruisers, nothing but beatings, starvation, mass slaughter, burning villages...and victory. Utterly incomprehensible, and utterly fascinating.