It was a brutal and disgusting crime- and the bloody death toll and horrible injuries that the suicide bomber wreaked upon the innocent can only be condemned by any decent individual. There are no reasons and no excuses for the people responsible.
Alas, that the failures of the Russian power structures have allowed the emergence of this kind of Al-Qaida inspired evil. As Wiki-Leaks revealed, the US assessment of Russia is that it is now entirely in the hands of contending, largely criminal, elites. A convenient simplification would be to say that power is divided up between different Mafia families, who have different interests in different industrial sectors and in different parts of the country. These interests are balanced by negotiations and occasionally by violence. Thus the idea that the Russian government exists as a monolith under the steel will of a single leadership is somewhat inaccurate. The group of five or so individuals around Prime Minister Putin are only the largest and most feared of these contending elites. Strongly Mercantilist, these groups trade favours, and where necessary punishments. Yet there is no clear strategy- only the short term need to gain control over assets and to ship the income derived from these assets out of Russia as fast as is practical. Liquidity is king in the under invested and increasingly decrepit Russian economy.
Meanwhile there are large areas that have been excluded from the process of trading favours. In particular the North Caucasus has become simply a battleground where only the most brutal can maintain even the most tenuous foothold. The deliberate flooding of the area with weapons by "dissident" members of the army (which kills roughly 3000 of its own conscripts every year) has made the turf disputes in the North Caucasian Republics, whether Chechen, Ingush, Ossete or Dhagestani into a festering, if relatively low intensity, war. The latest bomb in Moscow is merely a symptom, and not the most deadly, of the roiling violence of the North Caucasus. Yet increasingly the Russian writ does not hold at all in that part of the Russian Federation. A combination of neglect and brutality has totally undermined the rule of law and the erosion at the centre has become a collapse at the periphery. As racist violence emerges in the Russian heartland against those from the Caucasus, it is hard to see how the two groups can share the same state for much longer.
Russia is fraying at the edges- yet the consequences may yet push the Caucasian Republics into a still more deadly pattern of outrage and revenge. In the meantime, the West, lead by the US considers that the "reset" policy towards the Russian state has been a mild success.
It has not.
Russia may not be the strategic threat that the Soviet Union was, but the appallingly cynical and corrupt Russian state that has been created on the ashes is unstable and occasionally malevolent. Those who are locked out of the Putinista system of contending Mafias no longer believe that they can achieve anything by peaceful means, and the level of violence is therefore likely to grow.
The attack on Domodedovo was a deliberate attack on foreigners, and more and more they will be targeted as a way of getting attention and of reducing Putinista access to outside interest and money.
A witches brew of religion and nationalism has been cooked up under the reign of the Siloviki. It may yet be the rest of the world that suffers the consequences.