My sister's kids were pretty compulsive users of instagram and had a large instagram group of 'friends' made up of JW's. I have a sense that instagram is pretty big in jw land. They would take any and every opportunity to capture the cool, noteworthy or unusual moments to garner all important likes.
I believe the protest provided just such an opportunity for young JW's at Excel & the photos of banners were likely passed to a greater audience.