As to the formation my guess gravitational lensing interacting with dark matter. Im shooting from the hip.
Others are speculating (if I read it correctly) this might have to do with the originating star being one member of a binary star and the rings associated with how its partner was torn apart in the events leading up to the blast, possibly in stages. That might explain why such a definite orientation to the double intersecting loops of the “figure 8” rather than seeing something symmetrical all the way around.
dont know nuthin from nuthin ‘bout this stuff but im gonna throw somethin out anyways... since the center of the rings are of different distances from the center of the super nova, could it possibly be 2 orbiting planets exploded causing the rings??