Hanzou
Grandmaster
I thought you were asserting that MMA's growth and the incursion of WMA (like boxing) was responsible for much of the decline. Did I misunderstand you?
That's definitely part of it. There's definitely other factors at play, but it's pretty obvious that MMA is being chosen over TMAs for a variety of reasons especially among the younger generation.
Throughout those articles a fairly common theme were older martial artists saying that the younger generation preferred MMA styles over the rigors of of TMAs.