Re: Breaking up might be good for Google
In all likelyhood i'd expect the following.
They'd fight tooth and nail to keep search and advertising as those are it's core businesses, and have been since before a lot of other stuff was added. They'd also keep their entire backend server setup as it's used to run these two key areas.
By keeping the server infrastructure (as it's required for their core business) they would also effectively lock in all split off companies to paying them still as no cost analysis would come up in favour of switching to Azure or AWS, there's simply too much work involved as most are heavily integrated with the google ecosystem already.
Now for the split of sections.
Hardware: Drop all the smart home stuff off into a hardware division, as "OK Google" relies on the google search engine to work, they'd maintain dominance for a number of years but could allow competition like Microsoft to set Cortana as a voice assistant for home. Most people will still select google as the default anyway.
Mobile: This would likely be android and their mobile phone setup. Google can still pay (as they have been) to be the default operator for other manufacturers. They could also continue to add features they want to android as it's open source. It's faking competition.
Webtools: This would be things like google drive, gmail, maps etc. They would make their money from advertising, when advertising bidding comes up either google will win, or a competitor will pay way above the odds and not make as much profit.
Media: Youtube, music etc. Same as webtools. google will lose out on the subscription fees but that's about it.
Basically there would be a lot of juggling, but nothing would really change. The only risk would be if a competitor bought out one of the separated businesses. For instance, if samsung bought out the mobile company.