If you had forgotten all about Slamball it's not just you. Totally forgot about it until I came across this video by Mike Korzemba
on YouTube. If you've never heard of it and I likely won't do it justice with this description, but it was sort of like basketball with football elements... and oh yeah trampolines. It hit the scene in 2002 and I believe Spike TV was the main channel that broadcast it.
Anyway you'll likely get all the info you need from the abive video, though it concentrates more on the demise of the sport. If you want to guess what was the main reason for its demise now and see if you are correct? Please feel free. I definitely didn't know why it disappeared. This is the first I've even heard of it years since I was flipping through channels and I saw basketball... but not really basketball.