Google Domains != Google Registry
This is not completely the same thing that gave us ".zip", ".app" and other top level domains.
Google Domains, which is being sold, is the registrar.
What's not being sold (for now) is Google Registry (also known as Charleston Road Registry - see https://icannwiki.org/Google#New_gTLDs), ie. the operator of several top level domains. But Google being Google, the question is how long they'll continue to do this before they're bored with it.