How is blood moved through our arteries even after the ventricular systole (the process that propels blood through the body) has ended?

The answer is the Windkessel effect.

During ventricular systole the blood is propelled outside our heart to reach the different parts of our body, but part of the ejected blood is stored in our arteries as long as their elastic properties are normal.

Imagine that you have a pipeline made of an elastic material, then you pour water through this pipeline but you poured so much water that the pipeline is filled within seconds, so in order to store more water part of the pipeline stretches, when water is used at the end of the pipeline the stored water in the stretched part will be able to move, but since that part is elastic, this meaning it has the capacity to return to its original size, it will produce a force when recoiling that ought to propel the ‘stored’ water toward the end of the pipeline.

This is what happens during the ventricular diastole, the recoiling of the arteries’ walls propels the blood through our system even when the heart has ended its ventricular contraction. Allowing the blood to get to the capillaries at all times, ensuring thus the blood supply.

The problem comes when the arteries had lost their elasticity and therefore cannot guarantee the constant blood supply to the capillaries. The lost of elasticity gives origin to a condition known as arterial stiffness which is associated with myocardial infarctions and strokes (the two leading causes of death in the developed world). Arterial stiffness arises as a consequence of aging and atherosclerosis.

Source: Berne & Levy Physiology, Sixth Updated edition.