The problem is that saying "ISIS did [X]" is almost entirely meaningless at this point, unless Abu Bakr al-Baghdadi explicitly announces that he ordered somebody to do this. There are so many ISIS wannabe groups and lone-actors, in Egypt and elsewhere, that claiming "ISIS did [X]" is almost as meaningless as claiming that Al-Qaeda did [X]. It's more like, some idiot, or group of idiots, somewhere in Cairo or whatever, decided that ISIS is awesome, and they want in on that shit, so they either got in touch with other people who supported ISIS via friends or friends of friends, and eventually organized a method of getting a bomb onto a Russian airline with shit security standards, perhaps with the blessing and/or assistance of some other affiliated ISIS members, either directly or indirectly via sending funding/resources.K. A. Pital wrote:ISIS will be so very fucked if it is a bomb. Russia has been bombing Al-Nusra and Jaish Al-Fatah, one of the Gulf state jihadist "ISIS-lite" creatures, but if it really was ISIS, at least in Syria they will be routed.
Either way, neither of the world's major super-powers involved in Syria seem to actually care enough to do anything about actually eliminating ISIS. Probably because at this point there's not much that can be done via air strikes that doesn't involve massive civilian casualties. Russia is only bombing Al-Nusra and other ISIS knock-offs because they operate closer geographically to Assad's territory than ISIS does.
Anyway, the only way to actually get rid of ISIS in a humane way is commit to ground operations (specifically the US really needs to retake Mosul sometime before the Milky Way galaxy merges with Andromeda...)