I believe 2005 or somewhere else in the mid 2000s was when it started, at least for videogames and not the entire internet.
>xbox 360 creates social gaming, achievements, reimplements DLC from the original xbox and brings many edgy 12 year olds, chads and tyrones.
>notably way more dudebro games
>the first overhyped garbage AAAs appear
>EA sports games become popular
>HL2's popularity makes steam a huge success, taking over PC gaming
>PC gaming becomes more focused around console ports and shovelware while PC games become niche
>G4M3RZ and G33KZ are born
>reddit is born