I would like to examine from my perspective as an acting coach, the reason Bobby Jindal's speech did not work. I have heard a great many theories espoused and none of them actually addresses the root of what made him seem so inauthentic in his prepared remarks and why he comes off better in live interviews. It comes down to the difference between "How and Why."
In life we have thoughts and feelings and then we find the words to express those thoughts and feelings. It is a straight line. In acting as in public speaking, we start with the words. What should the great actor and the great orator do? They should find the thoughts feelings that make them need to say these words. In short they should find The Why.
What is a common mistake? It is focusing on The How. The actor or orator in this case is thinking about How to make the speech effective. If you supply the Why, The How takes care of itself. What Jindal did is focus on How he wanted to come across. In acting I call this a General Attitudinal Choice. He thought of the effect he wanted to have on the audience. He wanted to come across as likable and friendly. He wanted the audience to think that he is a good guy, so he adopted a general demeanor of kind and empathetic. This is why he came off as condescending. No matter what he talked about the the pose was the same. He was trying to project his idea of a warm and friendly guy. Therefore he came off as patronizing.
Chances are that he didn't write the speech. He needed to find a way of making the words come from him. In order to do this he would have had to contact sources within his own life experiences and opinions that are in agreement with what he was saying. His feelings and expressions needed to travel freely. Instead he locked himself into a false demeanor.
Obama is effective because he is in the moment. He is helped by the fact that he is a writer. Chances are that he wrote some of his address to the joint session of Congress. In any case, Obama connects his real feelings to what he is saying. He therefore comes across as the real deal.
Jindal is by far better in his live interviews. Some of the pundits have been saying that perhaps he was more nervous about delivering the Republican Response than he was in his interviews on Meet the Press and the Today show. His nerves had nothing to do with it. In a live interview he is speaking his own words, so they naturally connect to his feelings. He also doesn't know what questions he will be asked and therefore cannot premeditate the shape of his answer. He has to listen and respond which forces him to be in the moment. That is why he is more believable in a direct exchange with a reporter. Some have also pointed out that he may have a hard time reading a teleprompter. That is also not the issue.
True emotions travel. This is reflected in body language and in the voice. Manufactured emotions remain static. If you look at Jindal's eyes and listen to his voice in the prepared speech, you can sense the hollowness. His pitch did not vary. His expression barely changed. He tried to have variety in his manner but it was predetermined for emphasis and to give the impression of a real expression. He chose was and/or coached on where to pause and what words to stress. None of this happened organically and he therefore came across as insincere.