To be more specific, no one but the author makes money off a Facebook or Twitter post - except through second hand reposting. That cuts all the "consultants" and "experts" out of the loop thereby endangering their livelihood. Think how much money Karl Rove made during the last election cycle giving his "expert" advice while he wasn't running for anything himself. As always, follow the money.
No, there are entire businesses. Kim K for a well known example has a number of people who she pays to handle the posts ‘she’ makes. That’s part of her PR. In truth, half the posts are probably written by those same people posting as her. Nothing new or surprising there.
Point being, far more than one person can and does profit from social media posting. The consultants etc are the same people with a different job title making the same money. It just passes through different hands. The nature of the biz is the same.