It could be related to increased moderator diligence in culling Apple threads today. Previously, the front page would become clogged the days new models were announced. # of upvotes on single threads is not particularly useful absent more context/ information.
Likely also related to the fact that this is arguably the first time than an iPhone release has removed a feature. The highest top-level comment in this thread is about the removal of the headphone jack, and that subthread alone has 644 comments.
Similarly, this year iPhone SE got even more upvotes (567) than all of these https://news.ycombinator.com/item?id=11330226
Maybe due to an upswing in HN traffic? Lack of other news today (it has been slow)?
I'm not sure this release was particularly exciting.