I didn't see it, but my guess is that what she said is more like:
"NBC has lost over two million viewers since Peter Jennings stepped down and then -- Tom Brokaw -- his show has lost about, I don’t know, two million viewers."
In other words, I suspect she meant to say Tom Brokaw and said Peter Jennings instead, caught herself, stopped mid sentence and corrected herself, and continued.
If so, the following would have been what she was trying to say:
"NBC has lost over two million viewers since Tom Brokaw stepped down, and then his show has lost about, I don’t know, two million viewers."
Furthermore, I suspect Olbermann knows full well that she simply misspoke.
Are you Julie Banderas' 8th grade English teacher no having to use a red pen to correct her sentence structure?