It is very similar situation to Russian ransomware gangs. They have a rule not to target Russian and sometimes Chinese companies and FSB will then let them operate. The thing is that constant ransomware attacks on companies in the last decade has forced victims to at least somehow adapt and become more resilient to such attacks. However Russian companies were protected and now Ukrainian hackers are able to penetrate them using exploits and techniques which were either patched or ransomwed into oblivion years ago.
Case and point - Attack on a submarine in Novorossiysk which was observed by Russian Navy security camera controlled by Ukrainians.