The Elven King that wants to backstab the dwarves is the central character that unites everyone to fight Sauron at the end of this age. The last Alliance of Elves, and Men is largely his doing. These writers don't even need to read the books, watch the movies to see how this universe deals with Oathbreakers.
This new Mithril plotline is a eye rolling moment that doesn't fit anywhere in the universe. The whole first age of the story is about elves screwing up everything trying to take back shiny objects.[/spoilers]