Can someone explain to me how this happened ?

I just can't seem to piece together why the current meta is the way it is. I never once imagined that there would be a day where League would transform into 20 minute matches of everyone just killing everyone reminiscent of a COD. Despite playing this game since 2013, there wasn't any indication (besides maybe the release of Yasuo) that League, a strategy based moba, would become what it is today.