Users flagged it. We can only guess why users flag things. In this case my guess would be that they don't want the inevitable flamewar, as well as "If they'd cover it on TV news, it's probably off-topic" (
https://news.ycombinator.com/newsguidelines.html). There can be exceptions to that (e.g. the recent submersible disaster story), but only if the topic can support an intellectually curious conversation.