The absolutely most bizarre thing is that, being "Chechnyan separatists", they attacked the US, precisely the one country they shouldn't have. An attack of Russia, while stupid in its unlikelihood to mobilize popular support for their country, would be at least understandable. Russia is, after all, raping their country every fucking hour. An attack of revenge, maybe against the military or police forces, would be what's expected.
Instead, they attacked the country which they should have tried to ally with, the US. With United-Statesian support, at least they could have a shot at independence, or at least some favourable publicity. There are plenty of reasons for that to happen [1]. The ironic thing is that, even though it was a passional, senseless move, the kind that no serious terrorist planner would consider, it could bring a better understanding, and better publicity for Chechnya in the West. I hope. Or maybe they just ripped to shreds the only good card their country had.
Every terror attack that is attempted, the more convinced I am of Bruce Schneier's views on terrorism: terrorist are fundamentally stupid, emotionally fragile, intellectually lazy people [2].
[1] http://www.theatlantic.com/international/archive/2013/04/wha...