Earlier quoted context omitted.
The two other videos that got posted alongside this one makes me think it was a "forgotten tape that just got digitized" type of deal. However, I can also see there being an element of trauma and just not wanting to revisit the footage on purpose. I know I have some pictures I never want to look at again, although nothing on this scale.
As someone who watched the second plane hit live on CNN, it was... hard. People who weren't alive or were otherwise busy that morning don't remember the uncertainty after the first plane. Everyone thought it was an accident. No one could conceive it was a deliberate strike. Everyone knew terrorists hijacked airplanes to fly to third world countries, not to commit suicide into buildings. That cognitive dissonance all…
Watching it happen live with the immediate knowledge that it was obviously a deliberate act was, like you said, a huge amount to process all at once.
I actually think that having a goal like "get dressed and go to work" probably was a great benefit to my mental state.