In the traditional impression, the Russian tsar should be a Russian. However, boris Godunov, the third Tsar in Russian history, was not of Russian descent, but a Mongol. So why did Boris Godunov, a foreigner, become Tsar of Russia?

In the early thirteenth century, the Mongol Empire swept the Eastern European Plains with unstoppable force, and established a branch of the empire in Eastern Europe, the Golden Horde, and a large number of Mongols also migrated to the Eastern European Plain.
By the beginning of the sixteenth century, the Golden Horde had collapsed and its territory had been annexed by Russia (then known as the Grand Duchy of Moscow), and many Mongols had become Russian subjects, including the Boris Godunov family.
Boris Godunov came from a Russified Mongol aristocratic family that converted to Orthodox Christianity, and his father was a general in the forbidden army of the first Tsar Ivan IV.
At the age of 19, Boris Godunov joined the Forbidden Army. Relying on his father's connections, he soon stood out in the military. In 1572, at the age of 20, Boris Godunov married the daughter of the leader of the Forbidden Army, Skuratov, and this powerful marriage laid a solid foundation for Godunov's future prosperity.
In 1578, Boris Godunov was appointed by Ivan IV as a royal attendant to manage the Tsar's diet. Two years later, he was appointed imperial attendant in charge of the affairs of the Tsar's palace. From these appointments, it can be seen that Ivan IV had great confidence in Boris Godunov.
In the same year, Boris Godunov's sister Irina married the mentally handicapped prince Fyodor Ivanovich, and Godunov became the tsar's in-law.
In 1581, the enraged Ivan IV killed his son, Crown Prince Ivan Ivanovich. After Ivan's death, the Tsar had only two sons left. He intended to make his youngest son, Dmitry Ivanovich, crown prince, but the nobility considered Dmitry to be the son of the Tsar's seventh wife, and according to ecclesiastical law, only the first three wives were legitimate. Therefore, under pressure from the nobles, Ivan IV chose Fedoor as his heir against his will. In this way, Boris Godunov jumped from a relative of the emperor to a brother-in-law of the future tsar, and his status naturally rose.
After ivan IV's death, Fedoor succeeded to the throne. Boris Godunov also entered the core of the circle of power. Because Fedoror was mentally handicapped, military and political matters were often entrusted to Boris Godunov, who became the de facto ruler of Russia.
Boris Godunov was illiterate, but showed extraordinary wisdom in his power tricks and in governing the country. During the fourteen years of Fedoor's reign, Boris Godunov, on the one hand, dealt a ruthless blow to his political enemies, and on the other hand, he tried to keep the country in order, and proved his ability to the world with practical actions.
In 1598, Tsar Fyodor died. With Feodor childless, the Russians had to find a new Tsar. Under the circumstances of the time, Boris Godunov was clearly the most qualified person to ascend to the Tsar's throne. Thus, after some elections, Godunov became the third Tsar of Russia without controversy.
Boris Godunov was a diligent and capable ruler, yet his reign was fraught with tragedy. After the first two years of stability, natural disasters struck unexpectedly and led to severe droughts and mass famines.
The unstable environment caused turmoil in people's hearts, and the people began to circulate the rumor that Boris Godunov's usurpation of the throne only brought the country to heaven. Some careerists who were dissatisfied with the Tsar also wanted to move. Boris Godunov had to devote a great deal of energy to the battle against the naysayers.
Boris Godunov was a seasoned politician. Despite the extremely unfavorable circumstances for him, he defeated many opponents through clever means. However, just when many thought boris Godunov had turned the corner, he was poisoned and murdered at a court luncheon on April 13, 1605, at the age of 53.
Reference: History of Russia