If I was greedy and in the security field, with identities (or middlemen) on both sides of the game, I would be terribly tempted to play those identities to support each other. For example when blackhat-me would be selling an exploit, whitehat-me could create buzz by talking about it. Later, when the exploit's market value drops towards zero (ip enforcement is weak on the darknet), whitehat-me could reap the glory of discovering all the details about the exploit, maybe even using some "mistakes" blackhat-me left in the code to facilitate plausible parallel construction.

What are all those ifs having to do with the WannaCry situation? Probably nothing, hopefully nothing. Or maybe hopefully a lot, because it would mean that the FBI did not lock up the wrong guy?