Amstaffnole, (IMO) Don't think it's any one thing, but a combination of many things. People moved on to other interests, jobs, and locations. Others thought it was too cliquish, juvenile, and/or insulting. A few more got chased off by a no nonsense moderator. While others retired their "morphs." (Some posters did multiple characters with different screen names.) They have all but disappeared now. The Rival's national high school football message board is only missing a toe tag. Death could come any day now. You can access it at the top of the page under "Forums."
There is one hot national board started by the guy who ran the big Rival's message board. Dallas Jackson's "NationalHSFootball.com" It's the wild,wild west. Several old timers from here, Canes, OU112, DSouth, PL181, CatScatch, and another Cocoa guy?, DP, and a few more, battle state "homers" from Georgia, Ohio, Texas, New Jersey, California, etc. Everybody has an agenda in pimping their home state. Not uncommon to have 100 post on a single live game thread. Very large informative group of posters on all subjects, football or personal. Check it out. There currently (right now) several Florida threads going on. It is very entertaining. 100's of posts every day, 24/7, no BS. If you are easily insulted by vile written words the site won't be for you.