The "world" as most people on HN define it consists of the more stabilized parts of the Earth, perhaps because the participants in both HN and media come from those parts. So, I'll hazard a guess that the "world" cares more about French editors being slaughtered because it brings the violence uncomfortably close to home. Also, perhaps more people of the "world" can relate to the French editors than poor African villagers.

It's a sad state to be sure. Until we have some kind of common ground, it is harder to feel empathy. I will admit that I was much more shocked by this attack than the slaughter that you mention, which I even now know little about.