We're getting way too detailed in this thread and again much is wrong, although nice eye-candy. Again it doesn't add much to the thread subject regarding what failed and was uncontained , and why. The how and what fix is appropriate. is known by the manufacturer and the FAA.
There are many ways an inter-stage seal can screw up but causing an uncontained disk or blades in this case are unlikely. The interstage seal by itself can be liberated and be uncontained by spearing out through a localized hole in the engine case, like a spring hoop and be followed by broken blade debris in a shot-gun pattern. The seal itself may have sufficient energy to make it all the way across the distance to the other side of the fuselage by bouncing off the runway.
If more details of what actually did happen turn up then there may be room for discussion in this thread, but the videos above don't add answers to the fundamental questions regarding this incident.