For Leslie Moonves, the chief executive of the CBS Corporation, it was a week to savor. His decision to make Katie Couric the anchor of the “CBS Evening News” looked like a wildly successful bet, so far at least. On the entertainment side, CBS was set to go into the fall season as the most watched network in prime time. Success with another, equally fickle audience — Wall Street — endeared him to his boss, Sumner M. Redstone, the 83-year-old mogul who controls both CBS and Viacom. To top it all off, Mr. Moonves watched last week as Mr. Redstone...