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