With the google multi algorithmic approach combining, text metadata and popularity measures, the more people link to a site the higher it is in the search results and thus the more likely it is to be linked to.
People often place findability higher than content quality, if something is easily accessible, they will take what is easy to find and often give up looking further, even if further searches could have given them better results.
Networks – the greater the visibility the more likelihood of being found which further increases visibility.