Why did the Governing Body come behind the curtain?
To see what was on the other side of course.
Many have listed what I think are good reasons. Who is else is going to represent the WT but the GB? They are certainly deluded enough to believe that only they could truly represent the best of God's organization. If they were hesitant at first, it would only take some ego stroking to make them think that they thought of it first.
Now that the first act is over - breaking the ice and showing that the GB are just one of us - they will be quietly retired to the shadows lest any too human qualities shine though. Although it's a little too late for that. And by now, they are used to being on the throne so good luck with that.
Hey I just had a thought of how useful Warwick could be. Let everyone know that it is the place where god most often communicates with them. Have them permanently retire there. Then when groups of visitors tour, have them be seen off at a distance, giving a friendly wave. Except they are just Disney robots.