because he's the good guy and he felt guilty living him... i was really dissapointed in that episode tho... cartman just wasn't himself and the ending was just.....

I liked that ep. ,Kyle did it ecause he is a good person and they are kinda 'friends' now..

Cartman saved him in that episode ..i think it was called smug alert?When the Broflovskies moved to SF.

i think it's because Kyle kind of owed Cartman one because he saved kyle's life in imaginationland part 2 and smug alert, proving once again that Kyle is compassionate AF.