>>8046448well the entire concept of a board is a huge time expense
I think people just started leaving to tend to their lives, worsening the quality of the board, which then caused people to leave as the board wasn't worth their time, creating a downward spiral.
but I think we had the proper toolset to keep the board nice in spite of this before pepsibot decided to either make the board his bitch or make it unusable. That's another factor; I think too many people gave up on /bant/ when pepsi found the spambot code. Those two combined, I think, cause people to seek other pastimes, which is the concept you described in OP.