Rus is not Russia: it was a self-name for many different groups on that territory, and Moscow did not yet exist when Kyiv became a capital.

So very important to keep in mind that Rus is not Russia because that was a self-name for all multiple groups on that territory. And Moscow doesn’t exist at the time when Kyiv emerges as the capital. The first reference to Moscow comes from the 12th century when it was founded by one of the Kievan princes.