I think this may be a little misleading. By most accounts, overall interest in tabletop roleplaying games has been on the rise.

http://www.timesfreepress.com/news/life/entertainment/story/2013/jul/29/after-40-years-popularity-tabletop-gaming-ri/114446/

Interest in D&D has lowered in the roleplaying game community because there are so many other great options now days.