Edit: I’m not asking a rhetorical question. There are a lot of comments in this thread thanking “the mods” and I didn’t realize there was a mod team cultivating the front page. Can anyone attest to this?
> We didn't flag the post; users did. When it comes to submissions, that's nearly always the case - see https://news.ycombinator.com/newsfaq.html.
But there are other ways besides flags for stories to fall suddenly off the front page: software penalties (e.g. the flamewar detector, a,k.a. the overheated discussion detector, various abuse detection systems, etc.) and moderation downweights. Users don't do either of those.
These points are covered in the FAQ although necessarily tersely. See "How are stories ranked?" and "What does [flagged] mean?" - https://news.ycombinator.com/newsfaq.html