It happens to all topics.
One topic gets voted to front page, then people fall down the rabbit hole, posting any links they hit on their way down.
Once every 6 months or so Plan 9 gets a front page hit, probably from someone getting into Go-lang. Then we see all the related papers and websites flood in for a while - Russ Cox' site, cat-v, Rob Pike Interviews, Utah2000, The birth of UTF-8.
It's like the September that Never Ended.
The Story of Mel is on the same cycle.