I must admit that I am both fascinated and love Flat Earth theory.
There is something unique about it, since it is unlike any other conspiracy theory. There is no end game in most cases. It requires more than any conspiracy on who is behind 9/11, but it usually gives no gains to the people that are perpetrating it.
The other thing that also makes it wonderful is the fact that it is not about sight. In most conspiracy theories there is the saying "Open you eyes!" (sometimes with the addition of sheeple"). However in flat earth, sight is on the other side - look at this photo of the curve, look at ships on the horizon, so the theory recedes to touch, to feel. It doesn't have to make sense, it has to feel right.
I like the idea of flat earth, because it is such a distinct notion of not agreeing with sight in an age that is often called the most visual age in history.