The show is called rings of power. This show is based on Tolkien and he explicitly wrote about this and how it happened during the second age. You are going in circles now as this was already brought up as to why this isn't a mystery and we know all of this has to tie into the LOTR books. They are just making up their own version of the story and that is the only 'mystery' at this point in how different it is going to be from what Tolkien actually wrote. The 'gaps' in Tolkien are more along the lines of telling the narrative from a very high level and not getting into the finest details that would normally be told in numerous individual books set during the second age.
So honestly there isn't more to be said that hasn't been said before.