How did the Russians eventually come in contact with the Byzantine Empire?

In the ninth century CE, Muslim travelers met Scandinavian Rus merchants in the middle Volga region. According to their testimonies, the Khazars, who controlled the steppe in the lower Volga region, were fighting the Rus vikings in an effort to prevent them from reaching the Caspian Sea. In the second half of the ninth century, these Scandinavian Viking warriors and merchants succeeded in subjugating, taxing, and partially incorporating the Eastern European Slavic population into their new state of Kievan Rus in the upper Dnieper basin, with its center and capital in Kiev. Kievan Rus also governed the cities of Ladoga and Novgorod in the north and therefore controlled the famous riverine pathway known in Russian historical tradition as “the Path from the Varangians to the Greeks.” “Varangians” meant Vikings, or Scandinavians, and “Greeks” meant Byzantines.
Prevented by the Khazars from expanding towards the Caspian Sea and completely taking over the thriving trade between eastern/central Europe and the Muslim Middle East, the Rus Vikings instead expanded further into the areas of modern-day Ukraine and the Black Sea region; this expansion brought them into direct contact with the Byzantine Empire, whose territory in Asia Minor included the southern coast of the Black Sea; the Byzantine Empire also had outposts in Crimea. In 860 CE, the Rus Vikings unsuccessfully attacked Constantinople, the capital of the Byzantine Empire. In the tenth century, the Byzantines signed two treaties with the Rus Vikings; the ancient Russian chronicle “L’etopis’ Vremennykh L’et,” preserves the text of these treaties.
In the middle of the tenth century, the Rus ruler Sviatoslav defeated the Khazars; he then attempted to create a new power base in the Balkans, but the Byzantine army forced him to withdraw. His mother, Olga, was baptized in Constantinople and his son Grand Prince Vladimir adopted Eastern Orthodox Christianity from the Byzantine Empire (988) and became an ally of the Byzantine emperors. In this way, Kievan Rus joined Georgia, Armenia, Serbia, and Bulgaria in becoming an integral part of the Byzantine cultural world, which historians call the Byzantine commonwealth. At the same time, the Slavic and Viking populations of Rus were merging; they would eventually become Russians, Belorussians, and Ukrainians.