Something must of happened, besides just the shock of her name beimng announced. If you watch the clip, Ryan announces Mandisa, and the jeers start building, then complete silence, shocked silence.
If the audience was reacting in shock to Mandisa's name, the silence would of come 1st, as they processed what they were hearing, then the jeers would of started. But the jeers started, and then HALTED. Then, everyone, slowly gave her a standing O. You can see the other contestants, looking around, in shock and horror.
As for why this did not make it onto major news media, I am glad. It would only incite anger and things might get ugly. It may also encourage other pigs to try and do the same thing, for the media attention. The girls who did that do not deserve one second in the spotlight.