There is no bridge over the lagoon. There's the monorail platform, but that's not the view and the monorail can go down frequently, or be very crowded on the platform. Since that image was taken by a Disney photographer, it was likely after hours and from an area not accessible to guests. You can see the Matterhorn from the former motor boat ride platform between IASW and the Fantasyland side of the Matterhorn. It's now a seating area and would likely be less crowded than anywhere else with a view of the Matterhorn.