They could have used a VPN to connect to Proton and paid for their account with bitcoin or cash and then law enforcement would have had a very tough time. Instead, they paid with a method connected to their identity. Of course Proton handed it over when law enforcement came knocking.

If you don't want info being given to law enforcement by third parties, your best bet is to make it so that nobody else has access to it in the first place. You might get away with third parties that are in a jurisdiction unfriendly to wherever you live. Definitely don't hand over your info to a company in fricken' Switzerland and then be surprised when they comply with law enforcement requests for it.