Why did ISIS - ISIL attack Moscow yesterday?

EBL: Over 130 murdered in Moscow yesterday by ISIS 

Why ISIS - ISIL attacking Russia? Becuase they are working with Iran? As always with Zeihan, YMMV. I agree that this is a failure of Russian security forces.

Instapundit: PJ Media: Who is behind the attack? and Russia Attack: Can Biden connect the dots?

TOM: Death Toll Mounts in ISIS Moscow Attack

Australian Broadcasting Company: Why Russia?

Al Jazeera: Why is ISIS attacking Russia?

Did the Russians capture ISIS terrorists?

Instapundit: Can Russia continue to fight Ukraine?, Russia helping Iran, Moscow ISIS: Only surprise it hasn't happened here yet, Putin Blames Ukraine, Mass terrorist shooting at Russian concert