Truman was advised to identify himself with The New Deal coalition who were progressive intellectuals, urban blacks, labor, farmers.
He issued executive orders against racial discrimination in the armed forces and federal employment.
The Dixiecrats also called States’ Rights Democrats, opposed federal regulations because they considered interfering with states' rights. All these reasons gave him the black support needed to win the election.
Communities & villages: extended families. Trans-Saharan trade began with transporting food and necessities across to other settlements which in turn started more.
It simply makes no sense that a person would choose to migrate towards a country where the cost of living is high. Usually the motivation to relocate is precisely the opposite: the living conditions, employment opportunities and wages don't match the cost of living in a certain region and that prompts migration.