He wasn't one of their own. He was one of Putin's. You don't get invited to attend a special gala for the Russian propaganda "news" outlet, Russia Today (RT), and be seated two chairs away from KGB/FSB Putin, if you're not someone very special in their eyes. Check out my post above if you don't know what Russia Today is.
“Seated next to Simonyan at the dinner and just two seats away from Putin himself was perhaps the most intriguing example of how the Russians have gone about recruiting disaffected members of that establishment: a rugged-looking man in a tuxedo who less than 18 months earlier had been head of the Defense Intelligence Agency, the Pentagon’s powerful in-house equivalent of the CIA.
Michael Flynn, now a private citizen after a reportedly disgruntled retirement, was not there to gather intelligence. His attendance at the RT [Russia Today] gala, before which he also gave a talk on world affairs, appeared to inaugurate a relationship with the network—presumably a paid one, though neither Flynn nor RT answered queries on the subject.
Flynn now makes semi-regular appearances on RT as an analyst, in which he often argues that the U.S. and Russia should be working more closely together on issues like fighting ISIL and ending Syria’s civil war.
“Russia has its own national security strategy, and we have to respect that,” he said in one recent appearance. “And we have to try to figure out: How do we combine the United States’ national security strategy along with Russia’s national security strategy, despite all the challenges that we face?”...”