This article contains a fair amount of neoconservative cant, but it asks and answers an important question. From Andrew C. McCarthy at nationalreview.com:
There appears to have been no basis for a criminal or intelligence probe.
National Security Adviser Michael Flynn was dismissed amid a torrent of mainstream-media reporting and disgraceful government leaks (but I repeat myself). Among the most intriguing was a New York Times report the morning after Flynn’s resignation, explaining that the former three-star Army general and head of the Defense Intelligence Agency was “grilled” by FBI agents “about a phone call he had had with Russia’s ambassador.”
No fewer than seven veteran Times reporters contributed to the story, the Gray Lady having dedicated more resources to undermining the Trump administration than the Republican Congress has to advancing Trump’s agenda. Remarkably, none of the able journalists appears to have asked a screamingly obvious question — a question that would have been driving press coverage had an Obama administration operative been in the Bureau’s hot seat.
On what basis was the FBI investigating General Flynn?
To predicate an investigation under FBI guidelines, there must be good-faith suspicion that (a) a federal crime has been or is being committed, (b) there is a threat to American national security, or (c) there is an opportunity to collect foreign intelligence relevant to a priority established by the executive branch. These categories frequently overlap — e.g., a terrorist will typically commit several crimes in a plot that threatens national security, and when captured he will be a source of foreign intelligence.
Categories (a) and (b) are self-explanatory. It is category (c), intelligence collection, that is most pertinent to our consideration of Flynn.
To continue reading: Why Was the FBI Investigating General Flynn?