Flynn wrote a nauseatingly pro-Islamist op-ed that appeared on ELECTION DAY. It was just bizarre. He was a loose cannon and it was only a matter of time until he got fired, IMO.
The drumbeat that “Flynn was fired because he lied to Pence about a call with the Russian ambassador” always struck me as absurd, and as an excuse.
It appears that it was a convenient cover story. Loyalty is a two way street. Trump wouldn’t turn on a trusted advisor for a miscommunication between Flynn and Pence. It was obvious that there was a hidden reason for the sudden firing.