Here's my theory.
In the 80s and 90s, shows were made to promote the games they were based on. Then shows started to be made that were about videogame culture in general along with digital cyberspace type shit. This was way before large social media sites as we know them today and before Youtube.
Around 2010-2011, there was an eruption in the amount of streamed gaming content on Youtube and then on Twitch with players not only playing the newest video games, but also creating a parasocial relationship and responding to what their chatroom says as it happens.
Think about it - you're a ten year old boy and you like videogames. A lot. What are you going to choose?
A) A show about videogames except it doesn't feature anything you recognize with new episodes at the mercy of scheduling or production time needed to make more. The network executives hope that you buy the merchandise they don't have.
B) This guy who streams all the newest games on Twitch four times a week for hours at a time who you think is hilarious because he says fuck and yells a lot and even talks to you ("hey chat!"). This inspires you to play the same game and buy the game itself and maybe as much as the game's price for cosmetics and DLC.
I guarantee you out of 100 kids, 95 would pick B. TV is no longer about a TV show competing with other TV shows on a network, or against other networks, or even against streaming services. It's about competing with other entertainment mediums like online gaming. It's not a matter of shorter attention spans, it's about access. Games are immediate and interactive. TV is not.