During user research, we found that many users were not discovering any of the links on the left-hand side of pages. But they often gravitated toward the bottom of the page, especially the footer area, looking for the additional information.
We also wanted to use more of the page for features such as the Cast list and Filmography. Since the last redesign, we received a lot of feedback that the filmography was too cramped in the center column, and it was hard to read. So going to a two-column layout (one wide, one narrow) gives us more flexibility to show extensive content. It's also more consistent with other pages on the site, such as the homepage, the photo gallery, and the video gallery.
Additionally, we've received positive feedback that you can now see the entire list of additional navigation options in one screen without having to scroll down the left hand side of the page.