So I watched "The Great Hack" https://www.youtube.com/watch?v=iX8GxLP1FHo ...  

There is a mistake running through it, which explains why they are constantly surprised by their discoveries.  

Facebook is not (if it ever was) a platform for connecting people and sharing.  It is a platform to advertise things to people.  That is, to persuade people. 

Once you make that shift, it's all just obvious.

It's like Vance Packards "The Hidden Persuaders" or Adam Curtis "Century of the Self" had never been produced.