The problem is that Digg, Reddit, Facebook and, depending on how you look at it, Google were all founded by technoutopians with libertarian streaks who felt that
A) Censorship is bad
B) Censorship is also really hard but
C) See A therefore
D) No censorship of anything ever for any reason unless The Man demands it in which case I guess will figure something out but (B).
The trolls figured out pretty quickly that they could be as humungous dicks as they wanted to be because (B) masquerading as (A). The trolls also noticed that nothing upsets the normies quite like using a bunch of racial and ethnic slurs so they used them a lot. This forced the technoutopians to engage in a whack-a-mole of attrition because (B) so they doubled down on (A) until it became apparent to everyone that social media couldn't fucking shut down nazis.
Even the nazis took notice.
White supremacy jumped from Storm Front to Twitter and Reddit because they figured out they didn't have to hide anymore. Nobody could do anything. And websites designed to spread ideas and pictures as if they were contagious spread hatred like it was contagious.
Nerd laziness. That's what got us here.