Something we need to know about those Russian intelligence officers
The ones that the Trump campaign was in touch with, repeatedly, per today's NYT report. Let's call them group A. Were they the same people who were expelled from the country in December 2016, i.e., the group of 35 Russian spies on the list of "sanctions" - group B?
That would make sense - the very same spies who coordinated and connived with Trump's team obviously came up on the counterintelligence radar in early 2016; after the scandal broke about Russian interference in the election later in the year, their names would feature prominently on the list of candidates for expulsion.
It's very important to know what the correspondence is between groups A and B.
If they do overlap, as I strongly suspect they do, that casts Flynn's communications with the Russians in an even more sinister light. Was he promising that the Trump adminstration would re-admit group B to the United States because they were also group A - the group that helped Trump win the White House? (That would certainly explain, too, why Putin did not retaliate by expelling our own people from Moscow, as has always happened in the past.)
It's important to realize, too, that the Russians who were PNGed (persona non grata) in December presumably were spies in the Russian foreign intelligence (SVR) and military intelligence (GRU) services. Highly trained, high-functioning, dedicated, the crème de la crème working to serve the interests of a hostile foreign power. The reason why Flynn would stick his neck out of them really gets to the crux of Trump's own treachery.
Hopefully, the media will start raising such questions soon enough.