Do you need to go back? What exactly are you going back from? Is it not serving your needs? There are plenty of alternatives to Google services; I’d be happy to provide some suggestions, if you’d like, having been through this ever since The Snowden Affair.
IIRC, this was because the user in question had set a recovery email for their account, which Proton either volunteered or was forced to give to the authorities. Definitely crappy behavior on Proton’s part. Don’t set a recovery email!