The funny thing is it wasn't even a true shutdown - Cloud Domains continues to be a reasonable registrar with proper IAM management so actually much nicer than Google Domains for larger projects. There were plenty of docs on migrating which was a one command thing (don't think there was a UI). Non-"consumers" had a reasonable out, which they could then drop for another provider if they felt a need, but there was definitely no requirement to end up at Squarespace.

But they never marketed it, among all the backlash over turning down Google Domains there was never any true call-out to this. To this day I suspect many people don't know about Cloud Domains (which still exists and accepts new domains). I can't fathom any user-related reason for this - the contract in selling to Squarespace must have forced Google to be unable to properly market Cloud Domains as a transition option. If not, the Google Domains PM truly didn't know the existence of Cloud Domains?