They became experts because they write and publish and others agree with their writing and cite them in other writings. So, experts often become experts by popular vote of their peers. A similar occurrence happens on the Web. Web pages tend to cite other Web pages. The Web is a non-linear, unstructured repository of information.
Most Web pages have links to other Web pages.
These links amount to popular votes as to the authenticity of a linked-to Web page. One approach of Web quality research is to define Web pages as authorities or hubs. An authority is a Web page with in-links from many hubs. A hub is a page that links to many authorities. A hub is not the results of a search engine query.