Let's also consider something very obvious here -- if you were out looking up at the sky with a camcorder, and you were filming the space shuttle hurtling sideways through the air in a doomed re-entry, would you zoom out so that you could no longer see the object in detail?
1. They didn't know it was doomed.
2. They zoomed out because they saw a second trail and wanted to get it in the picture.
3. From what I read, WFAA was setting up for a different shoot, and the camera guy took the opportunity to shoot the Shuttle, too. Sounds like he used his pro-quality camera.