According to your question,
As per history, Prince Vldamir sent his emissaries to various countries to learn about their religions because felt that Russia would become a unified nation if it has its people practicing one single religion. The prince chose the Byzantine faith of Orthodox Christianity as the faith to bring his country of turmoil into harmony.
Also, this Christianity was introduced into the East Slavic state of Kievan Rus by the Greek missionaries from Byzantium in the 9th century. When Russia layed under the Mongol rule from the 13th through the 15th century, the Russian church enjoyed a central position by obtaining the immunity from taxing heavily.
