I've posted various explanations about this over the years - a bunch are at https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so.... Some good threads to start with might be https://news.ycombinator.com/item?id=21607844 and https://news.ycombinator.com/item?id=22902490. Also https://news.ycombinator.com/item?id=17014869, which shows how far back political discussion goes on HN, as well as the argument about politics on HN.
If anyone reads those past explanations and has a question about this that I haven't answered there, I'd be happy to take a crack at it.