It really was popular because its humor was so “fresh.” This was just before internet/youtube culture took off and most Americans hadn’t seen such a dry, peculiar film about their own culture. I fucking love it but it’s certainly not for everyone, that’s for sure.
It’s truly a film about not judging the book by its cover and allowing for that to happen instead of taking the film literally you can see the themes and especially satire/parody of the American dream as described above.