I don't think the Enigma machine example applies here.

The nazi communications were decrypted by a highly centralized and secrative group, making it very difficult for the Nazis to figure out how they were doing it.

But in this case any vulnerability in the ransomware will have to be exploited by many of the affected people to decrypt their files, which means wide distribution, which means that a leak to the ransomware developers will happen sooner than later. If there is no wide distribution of the vulnerability, the ransomware developers win anyway.