That being so, it might not be too preposterous to consider discreetly asking the Brits what they might have in a folder somewhere on calls and other contacts made by Flynn. As Flynn was known to be in touch with senior government officials all over the world, GCHQ might well have content or corroboration that NSA could have missed. Pull together enough “foreign sourced” stuff that way, imply something possibly untoward about all of it, send it on over to the CIA liaison, and you have a prima facie case that would satisfy the admittedly willing-to-be-convinced Obama Justice Department that Flynn might be up to something that could potentially damage national security.
Enter the FBI at that point to open an investigation. And focus on the Russian aspect as it supports the official Democratic Party narrative that “Putin stole the election”—and also satisfies the many in Congress, the intelligence community, and the media who are opposed to any détente with Moscow. It all looks and smells good because key evidence comes from outside the system and doesn’t appear to derive from dedicated players harboring agendas on this side of the Atlantic. Pull it all together and it accomplishes three things: it enables an investigation of Flynn, provides cover for media leaks, and both embarrasses and weakens the authority of the new administration.
Yes, I know this is largely speculation, but former colleagues and I have come to suspect something does not smell right with the Hannigan resignation and would seem to be quite plausibly related to Flynn. It also explains how and why the investigation proceeded as aggressively as it did: information derived from a major foreign intelligence partner could not be easily dismissed or ignored and would have to be acted upon.