Repost are usual https://news.ycombinator.com/newsfaq.html and sometimes the same link is ignored one time and gets traction other time. It's matter of the day of the week, the hour of the submission, the other post that are trending, the number of users reading the newest page, the phase of the moon, and many other factors. Just assume that it's a mater of luck.

Linking the old post is useful when it has some interesting comments (I sometimes quote partially the most interesting comment.) But in this case the older post got only 2 points and no comments.