Last time I checked, hacking was still a crime in most jurisdictions - even if the target is considered a geopolitical adversary. This sort of activity is also against the Proton ToS. Once KrCERT and Proton were alerted to this activity, they would have been legally obligated to act.

That's not to say I feel any sympathy to the target - who by all counts has done a fair bit of damage. But this sort of hacktivism / vigilantism simply isn't helpful. There's a high likelihood that one or more nation states / law enforcement agencies may have had active operations directed against this threat actor derailed by such activity.

tl;dr - If you're going to conduct such activities, practice proper OPSEC. And don't let your desire for attention / recognition take priority over staying on the right side of the law.