"What person/persons/group is behind the rebranding of Jehovahs Witnesses"
Why Jehovah God of course!
Seriously, I wish I knew. I think the main reason for the rebranding is to save and create cash to pay child abuse victims. This organization has always had money, but I highly doubt that they had tens of millions of dollars laying around just to pay out claims. Money is being saved by closing branches, consolidating and moving the world headquarters out of New York City, selling off kingdom halls, encouraging everyone to download their literature as opposed to getting books and magazines, I could go on. When a company sells and consolidates suddenly, they are in dire need of money. If they don't pay abuse claims or don't have the money to pay, the governments may start seizing property.
Maybe the governing body is behind the rebranding and only the governing body. It does not take a rocket scientist to figure this out.