A lot of these ads are done either through freelance contracts or AI generated.
I know in the late 00s there was a company that would contract out work on a bunch of the internet ads. A friend and I would get batches of ten to fifteen to do at a time. We would knock them out in a day. It would take two days if they wanted multiple pictures to simulate video. Nobody at the company was checking anything. The company we subcontracted from contracted other people to make sure they fit the basic outline and met the tech requirements.