I don't know how they make money...
Previous discussion:
https://themargins.substack.com/p/taboola-outbrain-and-the-c... (https://news.ycombinator.com/item?id=20409693)
https://www.nytimes.com/2019/10/04/business/media/online-adv... (https://news.ycombinator.com/item?id=21175145)
The answer is "sleazy bottomfeeders", if the Taboola ads I've seen are any indication. Supplements, worthless insurance, colon cleansers, and the like.