I don't think this article explains it well. Google sells ad space on behalf of the publishers and also sells the ads on behalf of the advertisers. It also runs the auction that places the ads into the ad space. See this graphic
https://images.app.goo.gl/ADx5xrAnWNicgoFu7. Parts of this can definately be broken up without destroying Google.
Breaking those parts away from google absolutely wouldn’t destroy them, over the years I’ve been so surprised from googlers at most levels explaining how much money they make from all their different services. While advertising is absolutely a big one, it’s by no means the only one, and if i understand the situation correctly, the more advertising options that are actually viable for companies will not even kill their advertising business. But big business real doesn’t like competition.