Why are most globular clusters round or nearly spherical?

Globular clusters are generally round or nearly spherical because they are highly concentrated at their centers, with stellar distributions that resemble isothermal gas spheres.12

This structure is a result of the complex stellar dynamics within the cluster, which account for the orbits of individual stars, frequent encounters between member stars, and the gravitational influence of the surrounding galaxy. Because these clusters are massive and old—having formed early in the history of the galaxy—they have maintained this stable, symmetrical configuration over billions of years. While most appear circular, some clusters exhibit a degree of ellipticity, and a few, such as Omega Centauri, are noticeably elliptical.12345