Because both Nixon and LBJ knew the South Vietnamese wouldn't agree to being sold out, so LBJ was just talking BS? A member who left, Realpolitik (unsure about spelling) goes into detail in some of his threads about Nixon and his supposed sabotage. Nixon did the same thing in 1972, that peace was just around the corner.
Yeah, I think Johnson was serious about it but nobody else at the negotiating table really had any reason to care.