Even on the scale of molecules and nuclei the same curvature of space occurs. That is; the atoms and nuclei within will cause space to curve around them respectively.

The scale of matter does not change the fact that all mass curves space. Therefore, it is the same law of nature that causes the contraction of the galaxies as well as the contraction of huge cosmic gas clouds.

So it is the fact that space itself in contracting (curving inwards) leads to the contraction of the cloud.

The gas cloud has an increasing pull towards it's centre as it contracts space towards it’s centre. This pull results in peripheral gases and other debris being trapped in the cloud, resulting in a larger cloud. This increase in the size of the cloud results in a stronger inward pull, and so forth. It is easy to see that this is self-perpetuating process.

As this process continues the space and matter, especially that near the centre, becomes increasingly more and more contracted. This results in the formation of a protoplanetary disc. 

Until now it has been a mystery as to how matter has amassed to become stars, planets and moons. But the aforementioned self-perpetuating process provides a means to understand such formations.

 
Contraction of the inner space (of an extended mass), is not the same as matter’s movement towards the centre of a gravitational field. When space contracts the nearby matter will amass.

So even when it looks like there is no difference between contraction of matter and that matters movement through a gravitational field, there is a real physical difference between these two separate processes. 

This simple theory can also explain how planets and moons, in a protoplanetary disc, were created. And why this will continue to be the case.

When all matter near a gas cloud (disc) has been attracted inwards, the system no longer grows. The process of increasing space contraction stops.

When the gas cloud (disc) stops growing, and the process of increasing contraction has thus stopped, some of the mass of a disc cannot be pulled completely towards the newly formed central body (Sun). This mass can not be pulled further inwards because the increase of the contraction of space is powered by the process of cloud growth.

This means that there is a surplus of matter that cannot be contracted completely and will therefore continue to circulate in orbits around the new created Sun. It is from this surplus matter that the planets have emerged. The process repeats itself on a smaller scale and brings upon the creation of moons orbiting the now ‘central’ planets.

 So the process that created, firstly the Sun, and then the planets will repeats itself, albeit on a smaller scale, in the creation of the Moon(s). This theory supports the observational evidence of larger planets having more moons than smaller planets, and these multi mooned planets have varying sized moons. 

According to this theory we can see that the nature of gravity systematically works, and is almost 'programmed', to do a complete job. Astronomical coincidences are no longer necessary to explain the formal of a solar system.

The nature of space and matter has the ability to define a central point, even for the smallest imbalance in space-matter density. Gravity, therefore, automatically outplays itself in circular, self-perpetuating manner.
 
Therefore there is nothing strange in the fact that, even small variations in the density of the young universe was sufficient to trigger the creation of galaxies, solar systems, suns, planets and moons