The big deal like the real important questions are what no one is asking.
Follow the chain:
NSA (most likely) monitors all communications but priority goes to Russian and Chinese (the big players).
NSA discovers that a Russian is talking to someone in the USA. Normally the American remains unidentified for privacy reasons and also because it is against NSA’s charter.
Here’s where it gets tricky - someone (A) decides that the American is talking about a crime or committing one.
That someone (A) goes somewhere and states that an American talking to a foreign official is or has committed a crime.
Some other person (B) decides that someone (A) is correct and grants access to (A) to discover the American’s name.
Some one (A) then discovers that the American is an official in the Trump Administration - M Flynn.
This is big so (A) goes to others (C) and they decide to leak the info.
We now have a very select very small group who knows Flynn talked to a Russian. This info is compartmentalized and SAP only.
Who do they leak it to? Perhaps the FBI to begin a preliminary but secret criminal investigation or something. Or perhaps to the State Department who then leaks to the media.
Why are these people A and the rest doing this? Because they hate/despise Trump and Flynn.0 These people could be Republican or Democrats - but likely a political motivation would lead one to thing Democrat (then again Senate Republicans are calling for an investigation of DJT and his Russian connections).
Once Flynn’s action become public, what have they achieved? They have helped put one nail in the DJT Administration coffin, and they have greatly harmed the USA’s national security by revealing the leak and thereby the method and means (just after beginning to recover from the utter disaster Eddy Snowjob revelations of method and means to the Russians and Chinese) - whatever source NSA used to record the conversation is now useless, gone, never can be used again.
That’s the big deal, the 800- lb Gorilla.
The general public should not be aware of a transcript of the (taped) conversation between Flynn and the ambassador. The quick series of events are:
1.) Flynn denies speaking about sanctions with the ambassador.
2.) The transcript of the conversation is released (to someone in the media first) to prove that Flynn DID have discussions about sanctions (although it probably was a vague reference and not a violation of the law, as supported by White House counsel.)
3.) The leaker got what they wanted. This sh*t bag needs to be exposed and prosecuted.
Flynn insists he did not cross the line