“Offered no evidence” is factually untrue
What’s the more plausible explanation - that a practically non-existent irrelevant-for-years terrorist group running unsophisticated operations in Syria suddenly assembled an A-Team to kill 150 people in Moscow, or that the Ukrainian citizen(s) who tried to flee to Ukraine committed the attack at the behest of Ukraine, which is currently at war with Russia? A real mystery!
What does ISIS have to gain by this? Ukraine winning the war is at least less unlikely than the Moscow Caliphate.
The same as with any terror attack they committed I guess, I don’t see how attacking Moscow is much different than attacking Paris for them, they declared war on basically the whole world.