Conspiracy theorists are assuming the conclusion before the evidence is in place. You know just like religious people can make anything seem like an act of god. Or believers in Nostradamus make everything seem like he was right. The list of alternatives stories one can make in retrospect is more or less limitless.
If you have already decided that the government are conspiring against their citizens then you will take any weird phenomena and use that as an argument for you case.
But you could might as well make another conclusion far less spectacular yet as horrific. For instance that the US government knew something was going to happen and they let it happen.
This would be a far less outrageous claim to make even though it's really pretty much wrong.
Conspiracies look like those that Wikileaks expose once in a while. They aren't well orchestrated, they aren't masterminded, they are messy, with lot's of potential leak risk and more importantly they are very small in scale.
Yet wikileaks have managed to get a hold of that.
One would think that if there are people who leak videos of US pilots shooting down journalists, there would be people leaking a far greater story, requiring a far larger conspiracy involving thousands if not hundreds of thousands of people.
One would also think that if the government really was that great at covering up something a huge as 9/11 then they wouldn't make stupid mistakes like the ones that the conspiracy theorists seems to attach themselves too.
In fact one would think that if they made such fundamental mistakes as those that seem to be used as a proof for the conspiracy then the likelihood of the conspiracy being leaked would increase by many many factors.
Unpleasant to think about? Yes for the conspiracy theorists.
A reality: Very sadly yes!