For Android, having apps ask for permission for notifications is a very new feature (debut in Android 13 I think) so by default apps notifications were collectively permitted. It would be up to the user to explicitly go in and disable notifications after the fact. I think many people either didn’t know how to access the notification settings or just didn’t care enough to disable them.
From what I understand, Google One had its own persistent notification (left side) when using the VPN as well as the normal key icon (right side). So now it just has the latter.