That post was on the front page for about an hour and then sank into oblivion, probably because of the flame war detector (more comments than upvotes). This one was very interesting to a lot of people and stayed at the top of the front page for quite a while and likely would have stayed there barring intervention.
I agree that dupes are a problem when there was ample opportunity for discussion, but when the previous submission gets downed by the flame detector or gets flagged to death by bad luck it seems like it's only fair to let the second submission stand a chance at natural survival.
At this point, the previous submission is arguably the dupe and this is the canonical submission.
https://news.ycombinator.com/item?id=40677424