Google use page rank to figure out popularity of page, semantic analysis of content and manual overwrite of rank. If you are travel agency you create crap cont

Google use page rank to figure out popularity of page, semantic analysis of content and manual overwrite of rank. If you are travel agency you create crap content and you create links to said pages. You target specific keywords and since your overall page authority is high then your shitty reasult flood google. If you have price comparision website you get manually de-ranked because you compete with google shopping. If you have stackoverflow clone you rank very high because google can serve more ads on your page vs stackoverflow. Even if google do recognize that content was scraped from SO, they choose to make money. On some keywords olny way to rank in results is to directly pay to google. For some keywords whole page of results is payed advertisments. Just to highlight few mechanisms.