I’m speculating, but perhaps the thought would be that separating Google Search from the rest of the company would deprive them of the alternative revenue streams they used to maintain their market position? If I remember the ruling against them correctly, one of the key pieces of evidence cited by the judge was that Google spent like 30 billion dollars a year to have 3rd parties use their engine by default.
Yes, I believe the figure they cited was that Google earns 73% of their revenue through ads. I imagine what they would have to do is bust up the ad services in addition to the various departments of Google. Each new entity formed gets to keep revenue from ads shown on their platform maybe? E.g. YouTube gets spun off into its own thing separate from Google proper. They get to keep ad revenue from what is shown on their platform, but they don’t get to touch any revenue from sponsored search listings, or from banner ads on other websites, etc.
That’s an approach that makes surface level sense to me, but I am neither a lawyer nor a business bro nor a tech bro. So, I don’t actually have the faintest idea if my idea bears any resemblance to reality.