In short: somebody thought it was interesting enough to submit, and enough other people voted for it that it got to your attention.
That's it.
If it ends up with 2000 points and sits on the new page for 3 days, I'll be quite surprised, but strange subjects do that.
Because someone posted it, and others upvoted it, and it got enough upvotes while it was new to get recognized by the algorithm and promoted to the front page. Now you know, and knowing is half the battle!
And a lot of the time, this random section was the more active of the whole forum but that was ok because it didn’t impact the other discussions.
But those were less engaging than social networks i guess (which hn is) so here we are.
Off-Topic: Most stories about politics, or crime, or sports, or celebrities, unless they're evidence of some interesting new phenomenon. If they'd cover it on TV news, it's probably off-topic.
Or, if you want to be less philosophical: anything that other people would upvote and not flag.
Here's an example recipe page that does feel appropriate to me: https://news.ycombinator.com/item?id=48408854
I'm not trying to win any wars here, I only provided a possible explanation to someone's question. Culture evolves and that's fine, or maybe the ratio of technical vs non-technical content is actually stable on HN? I really don't know, but to me it feels like the the volume of random content and low-grade comments is increasing. Personally, I don't think that represents the spirit of HN, but my comment was downvoted so either I'm wrong, the culture has shifted, or the mainstream is already the majority here.
I'm a fan of the Caipirinha however, so thanks for the Tschunk recipe.