Personally I got the impression that Kornheiser's schtick was something that espn advised him to do in order to set him apart from others and draw in casual fans. I can remember him on Sports Reporters twenty years ago, and he knew what he was talking about back then - before attempts at humor for entertainment purposes drove higher ratings than serious discussions about sports topics.
The network knows that hardcore fans will watch regardless but their theory has been to add a 'non-expert' for incremental ratings. It's as if espn/abc has been attempting - and failing - to recreate Howard Cosell over and over again on Monday Night Football for years. The fact that they are putting Gruden in the both rather than a Kornheiser, Dennis Miller or Rush Limbaugh says that perhaps they have decided to move on from the strategy of packaging the game as entertainment, and instead shift focus towards the game that is being played.