> the one person involved who was explicitly not responsible

Not to condone revenge killings, but Nielsen was obviously part of this accident. It was his choice to work alone that night (rather than waking the other controller) and to allow the technicians to turn off most of his instruments, so the responsibility is partly his. He also issued the fateful descend command - had he literally stayed out of this, the Tupolev pilots would have followed the TCAS guidance and the accident would not have happened.