Why did Malcolm’s father believe that all blacks should return to Africa ?

From the text:

He believed, as did Marcus Garvey, that freedom, independence and self-respect could never be achieved by the Negro in America, and that therefore the Negro should leave America to the white man and return to his African land of origin. Among the reasons my father had decided to risk and dedicate his life to help disseminate this philosophy among his people was that he had seen four of his six brothers die by violence, three of them killed by white men, including one by lynching.