well, I think it has something to do with the Joes being "a real american hero". It was ok some decades ago, but somehow they never got the universalness feature starwars gained over the years. That could explain a little about its popularity loss.
I also remember seeing Joes in crappy lowbudget stores, they sold them everywhere! (in mexico). But after ARAH, it all went down, we saw VvV but like 2 years later, and there wasn't many products. If it wasn't 'cause of the movie, I think I wouldn't have seen the 25th anniv figures, and where I live there where like 15 different joes tops. Not even all the movie waves came (sad face). I remember asking a hasbro guy on a retail store about POC, he did not know what I was talking about.

so... I think its a little about the world changing and a little about hasbro doesn't wanting to make us collectors happy.