It could be a big story, but unless it's a discussion on a technical failure, it doesn't really belong on HN. Ever since the last big election cycle people have been more strict about not allowing political and world-news posts that aren't related to tech or hacking culture.
In the past big news often made its way to HN. I don't really care about trivial world news so I don't search tons of alternative news sources.
If a nuke was launched and exploded somewhere I'd still expect it to end up on HN despite not being tech news. So the requirement of significance for unrelated news to make it here has gone way up.
