By significantly reducing the cost of creating the advertisements. Want to air a commercial? You no longer have to have actors, sets, designers, costumes, etc. just ask AI to make you a commercial and describe what you want it to look like.

Consider all the labor and capital spent across all the advertising real estate in the world. Commercial, online ads, billboards, labeling. The inputs to make all these things are now greatly reduced. To increase productivity, it doesn't matter that the market is flooded, just that it's much easier to make these things.