Barbara Walters talked with a horrible lisp in the 1970s. I heard her that way at least once. Then she got over it. Probably with the help of a speech coach. Then Walters kind of talked with a quasi-British or New England accent after that which might have had something to do with it (the British hold their mouths more tense when they talk I think). Then Gilda Radner started her Baba Wawa caricature of Walters still in the 70s. They say Eleanor Roosevelt sounded horrible when she talked too. Until diction coach Elizabeth von Hesse taught Roosevelt to talk with a sophisticated blended American and British Mid-Atlantic accent starting in 1938. Anyone remember how Barbara Walters used to sound when she talked?
Speech therapy took a big leap forward in the late 70s/early 80s. I was back in it with the new approaches, and my stutter and lisp are greatly improved, unless under stress. it makes sense that someone on camera would take advantage of new methods.