They were both significant British ports chosen for their favorable location, benefited from economic network of the greater Empire while being protected politically and militarily by structures far beyond their local ability. Part of it was also geopolitics of the time that dictated which colonies were better development prospects due to competing spheres to influence, i.e. why HK was chosen over Weihaiwei. Schrewd governance and intersecting geopolitical interests allowed them to maintain the inertia after decolonization.