How was it possible for blanche k. bruce and hiram rhodes revels to become u. s senators from mississippi?

It is possible for Hiram Rhodes Revels and Blanche K. Bruce to become a United States senators for mississippi because African Americans controlled a majority of the votes in the Mississippi state government. It is possible to the two people to become a senators of the U.S because of the African American who controlled the voters of the people in the Mississippi.