You don't actually need to click on an ad or purchase something from an ad site in order for Facebook to make money selling ad space.
The moment these ads are loaded on the page, real time auction occurs, where advertisers place bids algorithmically and automatically, based on your profile. Facebook makes it's money by selling this ad space. It doesn't particularly care whether you click on them or not. But if they don't load in the first place, there's nothing for Facebook to sell.
The real insideous part is that advertisers don't need to actually bid on the auction to participate, and anyone participating gets to havest your ad profile. This is one of the big ways data brokers are able to build profiles on you. They can then do whatever they want with this info, and you'd probably never know.
This is correct, and the extra insidious part is that folks who are tech-savvy and privacy-conscious are more valuable profiles than normies, because we generally work in higher income jobs/industries. So whether we click or not is irrelevant, Facebook gets paid more for showing us ads than they do for typical normies.
and thats why you lock down your privacy, so they get nothing other than "generic privacy enthusiast #1000101010101"
That's not true. If your ad placements don't perform, people are not going to book them. If ads are loaded or not is also often verified by independent third party trackers that you have to embed on your page next to the ad. There's whole industries built on this stuff and it's not as simple as "we sell the slot and don't care if people see it or click on it".