Perlmonks and the community it created is loved because Perl is also loved. Perl's flexible and eclectic style make it easier and even fun to work with, yet Perl isn't a very popular language(compared to C, C++, Java...). This makes a more unique and closer crowd to move towards it.

And besides, with a name like PerlMonks, you know it's for the more hardcore perl programmers. People go to Usenet first because they're not interested in Perl enough to try somewhere else.