Thank you! This makes perfect sense: "A huge percentage of online advertisements are never seen by humans. They are viewed by bots–automated scripts that are opening web pages in a browser and pretending to be a human. Advertising scammers set up web pages, embed advertisements on those pages, and then pay for bot traffic to come and view those advertisements."

https://softwareengineeringdaily.com/2016/12/20/ad-fraud-res...