How Does Google Rank Pages?
Google looks out for in-depth and useful content written by experts. The policy prevents people from creating content on topics outside their area of expertise, as it could be traffic manipulation or cause problems for people looking for answers and help. With topic clusters (that show content depth), the content creators present their expertise on the topic. The coverage of content reassures the search engines that the writer knows very well the subject. It's a misrepresentation at times because even experts make mistakes, and quantity does not equal quality. Plus, the search engines would need an expert on every topic to assess what the website expert says, which is not practical.