The money is nbd, but it's much more important to Google (same as it would be for any of the other tech giants) to keep a certain streak going - 42 years now and counting since the government forced a large or important company to do anything even resembling breaking up. A loss here would serve as precedent (either legally, or at minimum in people's emotions) that you CAN force a divestiture. If Google can be forced to divest this business, why not Chrome, YouTube, or Android? Why can't Apple be forced to divest the App Store business, or Amazon be forced to divest AWS?

Great question. The adtech is what rigs the auctions for their moneymaker, the ads.

If they no longer own the adtech then their ad revenue suffers greatly.