As we mentioned before, we do not yet have a definite model of galaxy formation.
Astrophysicists often debate amongst themselves on this topic.
(This is how I like to think of it.)
However, research on the role of dark matter in the early universe has given way to the "bottom-up" theory of galaxy formation, which has been widely accepted in the world of science.
The bottom-up model sees the universe as containing cold dark matter(CDM).
~'Cold' refers to the speed of the dark matter's particles in comparison to LS.
There are irregularities in the CDM, which can be seen as anisotropies in the cosmic microwave background radiation measured by satellites and other instruments.
As the universe expands, clouds of gas and dust collapse due to these irregularities and the gravitational instability resulting from them, creating stars with extremely high masses.
These stars are thought to be some of the earliest structures in the universe.
So gravity plays a dominant role in the formation of galaxies.