Due to some observations of mine, I believe that Google has just changed their search algorithm to place an absolutely HUGE importance on the trust and authority of the root domain where your backlink is. Obviously, you can't get better than Google itself. They could have added a redirect script to each URL, but that would have been a lot of effort and they realized how dead the directory really was so they killed it. Google doesn't do anything that doesn't make them profit and every time they make a change, it's to grab more profit.