I worked once for a small company that had a social media marketing side (separate from what I did for them, but we sat in the same open space). From what I've observed, the social media marketing business mostly boiled down to our people writing reports which shown nicely growing metrics to customers who then happily paid. The metrics might or might not have been correlated with any real-world increase in profits, and really neither side understood any of that. But it looked believable, so customers paid.

I suspect a lot of that is happening in adtech these days - people with no understanding of statistics bullshitting each other with pretty charts.