According to the insider, which I named "X", "Flynn was removed because he was agitating for a strike against Iran which would have had disastrous consequences. That would have led to Iranian strikes against Western oil supplies in the Middle East, raising Russia's economic power as the oil price would have soared to over $200 a barrel, and the EU would have had to join the Russian-Chinese block, or not be able to obtain sufficient energy to survive. The United States would have been completely isolated."
When still on the job as National Security Adviser, Flynn, on the record, had already put Iran "on notice". That was, for all practical purposes, a virtual declaration of war. "X" expands on the ramifications: "Turkey is the key here, and Turkey wants a deal with Iran. The key danger to NATO is Turkey, as it does not control Serbia, and Turkey-Serbia undermines Romania and Bulgaria in an outflanking maneuver to the southern-southeastern part of NATO. Serbia linked to Russia in WWI and Turkey linked with Germany. Tito linked with Russia in WWII and Turkey was neutral. If Turkey, Serbia, Russia link together, NATO is outflanked. Russia is linked to Iran. Turkey is linking to Russia and Iran after what Erdogan perceives was a failed CIA coup attempt against him. All this was way beyond the capacity of Flynn to handle."
"X" maintains that the Obama administration opening towards Iran, which led to the nuclear deal, was essentially a tactic to undermine Russia's Gazprom – assuming an Iran-Iraq gas pipeline would be built all the way to Turkey and then connected to EU markets.