^ Yes, this is what I was trying to get at.
Not only that, but I think from the mid-90s onwards, J-Pop became much less Japanese and much more western. Of course there has always been a western influence in J-Pop, but not to the extent that it is today - I think that also has turned off people that are outside of that younger demographic. Before, J-Pop always remained very distinctly something that was Japanese but with some western influences in it however, today for example, you've got Koda Kumi releasing a song called BLING BLING BLING, lol.
Also, about the cd sales thing - it's hard to know whether the mid-to late 90s was the actual peak for sales or not because from what I understand, the method for counting sales prior to that was not very accurate.