The expansion of the universe is governed by the interplay between various forces and energy components. While the gravitational pull of massive objects like neutron stars and black holes is indeed strong, it is important to understand that the expansion of the universe is primarily driven by a different factor known as dark energy.
Dark energy is a hypothetical form of energy that is thought to permeate space uniformly and exert negative pressure. Its exact nature is not well understood, but it is believed to be responsible for the accelerated expansion of the universe. Dark energy acts as a repulsive force, pushing galaxies apart and causing the expansion to accelerate over time.
On the other hand, the gravitational force exerted by individual objects, such as neutron stars and black holes, is a relatively localized effect. While they possess strong gravitational fields within their vicinity, their influence on the overall expansion of the universe is relatively small compared to the cumulative effect of dark energy on cosmic scales.
To put it simply, the expansion of the universe is driven by the dominance of dark energy, which overwhelms the gravitational pull of individual objects. While the intense gravitational forces of neutron stars and black holes are significant on smaller scales, they do not exert enough influence to counteract the expansive effects of dark energy on the overall large-scale structure of the universe.
It's worth noting that our current understanding of dark energy and its role in the expansion of the universe is based on observational data and theoretical models. Exploring and comprehending the nature of dark energy remains an active area of research in cosmology.