In all honesty, I'm seeing this with a lot of gun forums lately. When I first started on the Internet back in 1997, there were gun forums everywhere. 2 of the biggest back then were the old shooters.com, and Hunt America. Both used to have thousands of members, but are now long gone.
Another thing I've seen happen, is a lot of them have become overrun with young guys who love to argue. Or as John Wayne used to say, "Short on ears, and long on mouth!" ARFCOM is a perfect example of this. And to some degree, Glock Talk. They both manage to keep going, and maintain a large membership, albeit with a high turnover. Both places have a revolving door that is constantly spinning at high RPM.
What I always liked about this place is it's comprised of mostly older guys, who saw everything through the same "prism", so to speak. But lately they've been going away one by one. Hazcat, FQ, and TWyacht to name a few. And now Tom. There have been many others. Times change, and people move on.
I think in general the Internet is changing. People aren't spending as much time on it as before. Texting with Smart Phones, Facebook, Twitter, Instagram, along with all of these other sites are pulling people away from forums in general. For me, like most older guys, the older I get, the less I like change. I guess it comes with old age, just like sore muscles and bad backs.