[vapcmjoo] Causes of World War I

A hundred years later, we still have yet to reach consensus about the cause of World War 1.  Meta: why?  Several possible explanations:

1. Information has been lost, or never recorded.
2. It is difficult to reason about alternate universes: if X were different, then it would have prevented the war.
3. The cause is known, but we don't recognize that we already know it.  The "proof" of knowing the cause is preventing similar wars later, and similar wars later have not occurred.  This is, of course, highly arguable, but the argument is that WWII was of a highly different nature than the First World War.
4. The conspiracy theorist: political forces are at work preventing reaching consensus on understanding the causes of the war.  Perhaps the agents that are responsible for the war occurring still have power, don't want to have their power exposed, and don't want to have their power taken away from them.

We don't even know what caused the 2003 Iraq War.