I think this needs nuance - yes, the destruction of the central power in Iraq gave the various nasties who became IS a place to coalesce and a target (the US, and anyone who wasn't IS in Iraq) to fight against.
But, Iraq was not the only place on the world that such nasties had a 'safe space' within which to coalese and a target to fight against - they were all over east Africa and in Central Asia and the Caucasus. Much like AQ in Afghanistan, the ideas didn't start there, they simply went there because the conditions were favourable, and without the destruction of the central authority and the civil war in Iraq, they'd have have gone somewhere else with a limited central authority and a conflict to get involved in - and theres no shortage of them in the arc from the Med to China.
Blaming the invasion of Iraq for IS is like blaming Martin Luther's fly posting for the St. Bartholomews day massacre or the destruction of the Monasteries under Henry VIII - a contributory factor certainly, but only one of many, and with some of the others being far more powerful/structural.
It's also worth noting that Russia, and the Soviet Union before it, had a problem with Islamic terrorism long before the first American soldier set foot in Iraq in 1991, let alone in 2003 - so claiming there's some kind 'kill switch' on Islamic terrorism in Russia (and well beyond it) had the invasion of Iraq not happend is facile beyond words.