I believe the biggest reason for it dying was that a schism appeared in our community. A few people had a public argument, sides were taken, words were spoken, feelings were hurt, etc. We had some people leave, and despite some attempts here or there, we had no new members to fill the gaps.

Another possibility is this place was created back before sites like Facebook, twitter, etc. Once social media came to prominence, some of us started communicating via other methods and we didn't check the forum as much as we used to. When your userbase is that small, it doesn't take much of a disruption to kill it.