Democracy says that this place is peopled with hackers and if the hacker citizens upvote a story then it is, ipso facto, of interest to hackers.
Mobocracy says that demi-hackers trickle in and start upvoting stories and posting comments that attract quasi-hackers. The quasi-hackers then attract non-hackers and you eventually no longer have a narrow community. The stories that appeal to the lowest common denominator then rise to the top, due to sheer statistics.