Why does nobody ask how this poor chap has lost his life, and who might have been responsible? Is it so obvious that nobody feels the need to point it out?

This is a very beautiful song, but for me a large chunk of the beauty lies in the ambiguity: I suspect that she's done him in, but I can't be sure. Why should she a mourner be? After all, she's (probably) killed him. And why? Well, because (reversing the lines) he was the world to her but she was nothing to him. Is that not the whole point of this wonderful song? Again, if I'm just stating the obvious I apologise for the noise.