I can't really put my finger on it, but trust me.
Blowing up shit here, or threatening to, is not going to put the far left in power.
(Actually, don't studies show that people vote more conservatively under threat? Or does that only work on Americans? It certainly makes me think more conservatively.)
I don't really believe terrorists think their threats will change things. (Or are they really that stupid and childish?) They just want to be able to blame the victim for whatever they end up doing out of sheer hate and bloodthirstiness.