Why was the audience at the final oratorical competition stunned by Stargirl's performance? How do you know they approved?

Susan (Stargirl) was one of the last finalists to speak at the final oratorical competition. The audience was stunned by Stargirl's performance because it was so unlike that of the typical teenage orator.
First, Stargirl began her speech by executing a pirouette, curtsying, and waving to the audience. This was highly unusual; most contestants were nervous and behaved accordingly. Then, Stargirl began her oratorical speech in a similarly informal way. She chatted, instead of giving a formal opening statement. 
Stargirl proceeded with the rest of her speech in the same vein. Towards the end of her speech, she dropped her voice to a whisper. The audience strained to hear her last words. Cleverly, Stargirl concluded her speech with ten seconds of pure silence before returning abruptly to her seat. The audience members were so impressed with Stargirl's unconventional performance that they rose to their feet shouting, clapping, and whistling. Their exuberant response shows that they clearly approved of Stargirl's performance.