This request was by the same sort of people that worked to hide the dissemination of 9/11 images and all the other images of the execution and aftermath of every MUSLIM Terrorist action in this world. They are likely not Muslims doing this quisling treachery, but they are sympathizers.
Sympathizers who will not protect you, get justice for you or avenge you. If they are in charge, you are own your own.
They might be afraid of video surfacing showing the truck driver shaking hands with police after he parked his truck at the staging point.
More likely it shows the truck trolling back and forth about ten times in the 24 hours prior to the attack, and those images would be highly embarrassing.
Shades of the Colgne Germany police scrubbing the New Years Eve rape-fest video footage.