Did this stop Putin from murdering x amount of journalists? I suspect chilling speech is the ultimate goal and some petty revenge as well. Also maintaining the perception of being a "strong man" ruler who does whatever he wants.
>There's really only one group large enough to do what they want
I think you're vastly underestimate the intelligence agencies of many countries here. The CIA bogeyman gets you instant upvotes on reddit/HN but the reality is that the top 30 or so nations have impressive intelligence organizations with far reaching abilities. Cutting an internet line at an embassy in London isn't exactly the moon landing here.
Until we hear some technical details of some vast and highly technical attack that only the US can perform, I'll remain skeptical of such claims. The reality is that cutting or DDOS'ing lines is a trivial attack. This isn't Stuxnet and you guys know it.
Messing with the communications capabilities of an embassy is not something done without a whole lot of possible fall-out.
I'm sure they wouldn't shed any tears but it's unlikely they'll try to draw more attention to themselves.
There's really only one group large enough to do what they want, damn the consequences.