It wasn't the best speech, though Barbara and Jenna probably didn't write it. And I agree that it wasn't delivered that well but please remember, these are two daughters who aren't used to speaking before millions of people around the country.
But Kate and Vanessa and Alex were able to talk alone and deliver more than one half-witted line at a time. And they aren't used to being in the limelight.
It was the low point of the convention. Arnold was the high point, he made be feel proud to be an American.