First, the websites that you are using are high PageRank (PR) social Web2.0 properties such as Google Knol, Quizilla, Hubpages
. These sites have high authority in the eyes of the search engines so those pages will often rank quicker and higher than your target webpage. Second, by building several different websites that contain your content, you increase the chances that you can have several spots in the top 10 results and, therefore, increase your chance to capture that traffic. It's not uncommon for a properly developed link wheel to secure 2-5 positions out of the top 10 spots depending on the keyword that you select. In the end, link wheels are an amazingly effective SEO tactic to not only increase your target website's ranking, but also to have multiple properties listed in the top spots of the SERPs.