I believe it's the current ebb and flow of things.
A lot of the popular powerlifters went to IT and brought their friends and some when to/started their own boards.
A lot of the remaining people have either become tired of posting up the same advice over and over, some have become frustrated to see their responses completely ignored or misconstrued with a follow up of seeing that very same question asked yet again in a different way. (Diet board has this problem at times too)
Many people are afraid to post in fear that someone who think they "knows everything" or that their way is "the only way" will mock them and their answer.
In short, I think we have a lot of lurkers right now, quite a few people that know what they are doing but are uncomfortable giving advice given the potential of hurting someone in giving bad advice. Not that the "boys" would care but most of the women post about training in the women's board.
So, rather than pointing fingers as to what or whom is to blame, take the time to figure out how to make it a better place.