The history of Christianity is described superficially, roughly, negligently. An example of this is the story of the spread of Orthodoxy to the east.
The author speaks a lot about Russia.
But the first Khrestians appeared in Bulgaria. In 865, at the time of St. Prince Boris, there is a universal baptism of the Bulgarian people.
Then Christianity came to modern Ukraine. Then it was Kievan Rus. The capital is the city of Kiev.
Prince Vladimir of Kiev was a pagan. Then he chose between different religions for a long time. He even leaned toward Islam. But in chose Christianity. And in 988 he accepted Christianity.
The city of Moscow appeared around 1100-1150. And the Moscow principality began to be formed only after 1277.Three centuries after the baptism of Kiev and Sofia.
The Moscow state was formed in the 15th century AD.