I don’t think that’s necessarily the way to interpret that graph. Look at 2:12:08 PM. It still has only 5 upvotes but gets placed onto position 26 of the best list.

Sometimes posts that had few votes get put on the best list and given a second chance. Looks to me like that’s how this story started getting more votes, allowing it to gain traction.

See also this post by HN moderator “dang” about the second chance system and the comments he wrote there as well about it: https://news.ycombinator.com/item?id=26998308