There is a detailed article in today’s Miami Herald on the history of the WWE-Kurt Angle split.
Kurt Angle always claimed he quit, but in the article, it is revealed that WWE gave him a mutual release when he refused to go into drug rehab.
The article also reveals that WWE had wanted Angle to go to rehab months earlier and he refused then too. This is significant because to this day Angle goes to media outlets and claims he wanted to go to rehab when in WWE, but they refused to allow him to, claiming he could just rehab himself on the road.
You can check out the complete article in the Miami Herald.