There are all sorts of nonsensical conspiracy theories running around ranging from experimental ray guns and nuclear experiments to the malign influence of supernatural forces. I don't subscribe to any of that nonsense.
The earthquake happened because of the movement of tectonic plates. In the case of Haiti, those plates were held static until the forces were great enough to make them move suddenly. That's WHY it happened, the movement of tectonic plates. It's no mystery requiring any more complicated explanation.
The tragedy is that such movements, although they are known to occur and we can identify points at risk (such as along the San Andreas fault), we can't predict when they will move suddenly, producing an earthquake.
Attempt to provide more spectacular, and nonsensical explanations rely on a loose association of events. For example, the idea that the US Air Force had something to do with it is speculated simply from the fact that they were in the area. But we could equally well associate it with a particular weather pattern, with a similar lack of any real reason.
We have to examine the real physical causes of these events and dramatic and deadly though it was, it's no mystery. No conspiracies, no dark forces, no supernatural beings behaving capriciously, no angry Gods, no magic, and in reality no mystery.