The theory might better explain how supernova remnants form. After supernovae explode, their outer layers are blasted off in all directions, colliding at high energy with gas surrounding the star, forming a ring of gas glowing in radio, X-ray and visible wavelengths. The rings are called supernova remnants. Now, you'd expect a supernova remnant to be nice and spherical.
Space is full of peculiar shapes like ducks, guitars, speedboats or jellyfish.
So the shapes of supernova remnants reflect the complicated environment into which they expand. They pump this energy into the ISM, which creates structure and turbulence. Supernova explosions also leave holes in the ISM, but much bigger. If the bubbles are big enough, they can break out of the disk of the galaxy and become 'worms' and 'chimneys'. The gas blown into space by the supernova explosion eventually cools to form molecules, which clump into very dark, dense clouds.