Veritasium had a really good video on how facebook benefited from people buying legitimate (not fraudulent, click-farm) likes from fb. [1] Its over 10 years old now, but really good.
Basically, you could pay fb to boost your fb page, which is the "legitimate" way to get more reach. The problem was that click farms would like your page anyway, Why? Bc liking pages they were not paid to like would help hide fraudulent activity. So if one click farm clicked many likes on one page, that would be eady to spot as fraud, so that same click farm would like many other pages as well, ones that fb customers paid to boost and also got in front of the same click farms.
This created a dynamic where buying legitimate traffic from fb would hurt reach anyway bc the algo would key off of engagement, which would plummet bc the click farms saw the post that the page legitimately paid for. But that just incentivized the page owners to pay for more reach, thus fb would get paid more - fb had no incentive to stop this and paying fb in the first place would be worse tha not paying them at all. LAWL.
I guess the moral is -- never pay for boosting. And makes you question the quality of meta's revenue.
But the flip sides is that many companies (mine included) rely on instagram ads for revenue.