He never registered google.com. google.com is hard-locked at the registry level by Verisign and has very high security manual safeguards around any changes that are made to it.
There was a temporary bug in Google Domains that made it appear as if he had bought google.com, but he had not.
Oh, this is available to anyone with a .com using a major registrar. I had misunderstood this to be some special feature only available to the domains that make up massive amounts of internet traffic like google.com.
There is likely to be even more scrutiny placed on any changes to domain names that employees of Verisign immediately recognize, such as "google.com". I imagine that would have to go through a very high level person at Verisign. It's in everyone's vested best interests here to not screw up something so visible as that.
There was a temporary bug in Google Domains that made it appear as if he had bought google.com, but he had not.