[josefresco]

I find, anecdotally, that topics or subject trends come in waves of 2 or 3. Something will make front page of HN, and then a few days later someone else will capitalize on a proven "market of interest" and submit another article that also makes it's way up.

Could also be a paid PR campaign if you're the cynical type. 50/50

[usrusr]

“Capitalizing on a proven market“, or maybe just simple, old-fashioned web "surfing". Following the links deeper and deeper into a topic originally found on hn. Hundreds venture off into the rabbit holes, a tiny fraction feel they found something worth sharing back to hn.

Most likely a bit of both, you are not alone in noticing the pattern.