What really happened on 9-11?

Okay, so I know I've seen this episode of South Park about 65 times. I Tivoed it and watched it repeatedly 'till my mom deleted it because the 9/11 song annoyed her after the 31st time I played it. But I always wondered, do 1/4 of Americans think 9/11 was a conspiracy? Are 1/4 of Americans retarded, as according to Kyle. Here's Cartman's explanation to 9/11:

"Remember that there are, in fact, 2 towers. 2-1 is 1. 1,1: 11. 2-1 is 1. 1,1. And there are 9 members on Silverstein's board of directors. That's 9,1,1: 9/11. And take 2-1 + 9/11 and you get 12. Which leads us all to the master mind of the 9/11 attacks…Kyle! Twelve contains the numbers one and two, just like the toilet yesterday where somebody went number two instead of number one! And one and two with 911 and you get 914! Drop the 4 and it's 91! Exactly the score Kyle got on his spelling test twelve days after 9/11! Who has the most to gain from 9/11?! Kyle! Who was nowhere to be found the morning the towers fell?! Kyle! "

Well there you have it. A 9 year old cartoon did it. Hmm. Interesting. I coulda sworn George W. Bush said it was terrorists. But then in the middle of the episode, Bush claimed it was a government conspiracy. Then they said the 9/11 conspiracy was a government conspiracy. W.T.F.?! Who did it? George Bush, Kyle, terrorists?! I went on 911truth.org which is the most confusing website since the FreeRepublic.com. I don't understand these politics sites but I'm guessing these people who run it are the 1/4 or retards who think it was a conspiracy. I tried reading an article titled '40 reasons to not believe the official 9-11 story' or something. I dunno, but it was so confusing. What do you think about 9/11??