First of all it sounds quite easy for a person to wear a 2 to 4 kg of TNT on a belt and take ride through Moscow Subway, since there are no metal detectors (and no easy way to put on every single exit for a metro system of around 180 stations and up to 8 million passengers daily). So I can believe that some suicide bombers (regardless of their ambition) can easily sneak into the trains. Nobody would quite catch on a woman with a big belly on a Moscow train since most of the thin-bellied supermodels you are accustomed along with the russian image would sure prefer their husband- or lover-sponsored SUVs up above the crammed roads of Moscow. But the security is not that lax, of course. As I have written in this blog for a number of times, the passengers with a darker shade of hair (the darker your hair gets, the more crosshairs you can feel on yourself) are more prone to regular passport checks. Although comparable neatly clothed than many terrorist wanna-bees from Northern Caucasus, I was treated like one of them several times by Metro police and trust me, they are not joking (or were joking but not showing, since they let two real bombers do their job).
Some eye witness reports I have seen on the Russian web claim that the "terrorists" were wearing traditional muslim womenwear (or simply, black cloth covering all but eyes) on the train. That witness must be on some narcotics or having post traumatic stress. Dress up like an Afghan woman on Kabul bazaar and hop on the Moscow Metro; I am sure the loyal babushkas (old Russian laides) would gladly hand you over to the police on the next station, let alone the free roaming skinheads or neo-fascists (I call them the cossupt grandchildren of the generation who fought fascism). So it is almost impossible for a suicide bomber to look like a "suicide bomber from Chechnya" and walk free during a Moscow rush haour (which is the closest audition for the Armageddon). It is also not easy to brand a woman as such, since during rushhour almost every single member of the nations walking on this earth are represented in the Moscow Metro trains: From Nigerians of the African deserts to the deer hunter Yakuts of Siberia. So you cannot say that the woman with black hair is a suicide bomber; otherwise I would be a thousand times blown to pieces before.
As a result, branding the Chechens (although I have no intention to fraternize with them or whatsoever) may not be to blame. First of all, their cause is already lost one, with a stab in the back (the clans which united against the crumbling Red Army and mass decapitated untrained Russian recruits during the 90s, are now fighting a quasi-civil war between themselves and El Presidente Kadyrov is the game master) and the remnant hardline terrorists have been either one by one hunted by FSB (Russian Secret Service or KGB-renamed) in their hideouts in Turkey or the Gulf, or already presented their loyalty to the Russians in fear or gold (You may have seen them fighting fellow Georgians in the latest Ossettian War). These bombing will not , in my opinion, add some popular support to their cause (because the extremist islamic hordes are the bad guys of today). They were already losing ratings after they slaughtered children in Beslan Shootout.
I think of a deep-state bombing frenzy that would make the lazy Russians regain their Stalin-era "consciousness": Create an enemy (preferrable an internal one), polarize the nation and hide the agenda....that worked before (ask Stalin or even Putin).
Let's see what they are hiding now. Maybe the oil wells dried up or the natural gas just went natural...I would start saving some foreign currency if I was Russian.