Trump received a dual-benefit from his incendiary rhetoric. Not only did his supporters ReTweet him, but so did his opposition. Whenever the opposition called him out on social media, they unwittingly gave ammo to the minority of followers who were quietly supporting Trump.

2016 was the BuzzFeed election. The mathematics of viral tweets is how Trump won. If a politician says something politically incorrect that irks the ears of 20% of the electorate but inspires or rings true for 12% of the electorate, they may still win if only a quarter of that 20% opposition shows up versus half of their 12% supporters.

With the mainstream media (i.e. CNN, national newspapers) disrupted by social media (i.e. Facebook, YouTube), it's no surprise that the winner was the one who could spew viral content on a daily basis.