The bottom line is, Cartman got the biggest laughs. He modeled that a certain type of behavior resulted in certain outcomes. Kids aren’t stupid. They see right through the overt morality (“he’s a jerk and he got his comeuppance “) to the revealed truths: being an asshole, in some contexts, can be very funny.
It's absurd to even deny it, Cartman was admired and emulated by a whole generation.