https://www.gsb.stanford.edu/faculty-research/case-studies/o...
https://en.wikipedia.org/wiki/Barack_Obama_on_social_media#S...
Your average person may not be on twitter I give you that- your activist however. They are very likely to be on twitter if not another emerging platform at this point. And the media is much easier to reach with Twitter. Just try getting organic traction on a press release with traditional media without social media. Its painful to think about honestly.
It all came down to in-person contacts. The Black vote didn't turn out because they saw a tweet, they came out because people knocked on their door and talked to them and convinced them to brave the cold and vote.
And just as crucially: the Republican vote didn't come out despite all of Trump's tweets, and Cruz's tweets, and all the other GOPers posting on social media. The Republican voters stayed home despite all the social media begging them to vote because the GOP didn't have the same level of in-person events for the runoff as they did for the general election.
Twitter and Facebook's bans of Trump are only news because Trump relied on them so heavily. They're not the primary means of communication for politicians, nor have they ever been.