The Meaning of Life, the Universe, and Everything.
1. They never moved
2. They did not "re-enact" 9/11, the scene in the the episode where those two towers get destroyed was made before 9/11 and was just released at a really unfortunate time, unfortunately people thought it was intended, were dicks about it, and got the show taken off-air for about two months!
3. You should "look up" the incident because what you said isn't what happened, the creator of this amazing project doesn't have time to deal with people like you!