I think it was a combination of things...cost of hosting, lack of activity, lack of interest (both members and admins), apparently the forum software had been so customized that updating it would've been a nightmare (even tho I thought it was fine the way it was), etc. They never did get the database (gallery, walkthroughs) put back together after the last crash (or whatever happened).
I know some folks were trying to archive as much of the forum as they could. I was kind of surprised no one stepped up to offer hosting...but then again, the interest just wasn't there.