It's conventional for there to be a thread on HN when a major pubic figure dies. If you look at the list of obituary posts on HN [1], several of the biggest were for politicians, royals, and others unrelated to computer science and technology.

It's in keeping with the convention that stories that have "significant new information" are on topic for HN, and that includes major mainstream news stories when they first break.

[1] https://hn.algolia.com/?q=%22has+died%22