The timing of this is very convenient for KGB Vlad. He just locked up some of the opposition a week ago after the first major protests in years.
Yes, and he probably blew up the ammo dump in Ukraine the other day, and he certainly assassinated Denis Voronenkov. This may be the rationale for putin striking out as some other country that had nothing to do with planting the bomb. This ally of the “civilian barrel bomber” (Assad) knows a lot about killing as a tool of statecraft.
Now what other country would do this.
And IIRC, the USA protested Russia's last election.