But my point stands - how did Flynn get unmasked?
This plea deal by Flynn is being presented in the media as if the prosecutors have a whole lot of leverage against him to make him cooperate with them to get higher-ups in the Trump team.
Actually, the exact opposite is true. The whole process of surveillance and unmasking is so fouled up from a legal standpoint that the evidence they collected against Flynn would probably never stand up in a court of law. I see this plea deal as an admission by Mueller's team that they can't possibly prosecute him for anything more serious anyway ... and the prosecution may have had to make huge concessions to Flynn in order to get him to agree not to take legal action in response to the abuses related to the FISA warrant that was used to gather the information against him.