This is a very important point. I haven't yet seen a satisfactory conspiracy theory that explains why anybody would pursue this sort of action in the full glare of international publicity, and it's hard to imagine someone being good enough to pull this off, yet not realize this would happen. There aren't many conspiracies that benefit from continuous, sustained attention of this scale, or that could plan on absolutely no incriminating piece of evidence being turned up anywhere, by anyone, on such a large scale.