The uber-liberal, victimization narrative is factually incorrect. The reason Haiti is lagging far behind is their own doing spurred on as it was by brutal family dictatorships. Now contrast Haiti with the Dominican Republic, which is on the same island and ask why "blacks" on that side of the island are doing way better off. In sociology the term is agency.
According to a study by the American Library of Congress, by the end of the 18th century, there were about 40,000 white landowners, 25,000 black or interracial freedmen and 60,000 slaves in the Spanish colony, compared with approximately 30,000 whites, 27,000 freedmen, and at least 500,000 black slaves in its French counterpart. So to answer your question as to the difference? Black people.
More investment went into the Dominican Republic not so much for the dark side.