This is why I like how Bluesky handles it, you can use your own domain name. So I simply got @gilli.is, no reason for anyone ever to take that away from me.
Someone, somehow is paying for bluesky's servers and data. TANSTAAFL.
Google was running my email server with custom domain for years, free of charge. I think that it is still grandfathered in for those that signed for Google Apps early on. IT doesn't mean that the "email is free".
That's just mildly exploiting the fact that social engineering on DNS infra is not yet popular. Once everyone starts doing that, the black hats just move onto the DNS platform and we will all be worse off.