If galaxies are created on strings which are electrically connected (helical motions) with some central knots, these knots specifically produces perpendicular magnetic fields which subsequently creates the galactic disks and gives these the rotational momentum.I don't know what induces the rotation within the galaxies, but they tend to be aligned with each other, in a ring around an extra-galactic void. So perhaps there is an extra-galactic magnetic field that induces the rotation.
You are talking of implosion/explosion but the very similar motions can be acchieved by electromagnetics. In my ideas of galactic formations, the initial motion is magnetic attraction of gas and particles via the galactic poles (holes) and assembled to large prototype spheres in the galactic core via the Bennet Z-Pinch effect (nuclear force) and slung perpendicularly of the electric current out of the galactic center, out in the bars (dispersion to stars, planets and moons here) and further out in the galactic arms as the Solar System.
Edit: If so, all issues of our Solar System should take this formation into consideration.
The barred structure in or galaxy shows an overall outgoing motion from the galactic center (just like a two arm rotating garden sprinkler) This motion confirms the observed galactic rotation curve and also the formation via an electromagnetic circuit.