If Apple begins blocking their trackers (see Google's recent worldwide Chrome ad campaigns - a campaign that likely sees the writing on the wall), they lose all Apple revenue.
If 10B market cap companies begin to campaign for antitrust, and Microsoft negotiates for Bing on Apple, Samsung, and Firefox, Google will lose everywhere else.
I honestly don't even see why Microsoft couldn't play equally dirty and revert Chrome's default search engine on Windows to Bing. It's an equally dirty move to the stuff Google has done.
Google could have a strong cloud product, but they're in distant third and aren't investing enough to take away AWS/Azure market share. Their culture of launching products for promo, launching competing products (eg messengers), and then killing them has severely damaged their reputation.