The object sold as a voodoo doll is not from Vodou. It is not used in Haitian Vodou, it does not appear in Vodou's own accounts of itself, and the association was manufactured elsewhere.
The actual antecedent is European. Image magic, making a figure to stand for a person and working on the figure, is documented across Greece, Rome, Egypt, the medieval Mediterranean and early modern Europe, and it appears heavily in the records of the European witch trials. That evidence needs handling with care, since confessions extracted under torture describe whatever the interrogator already believed, but the practice is independently attested in magical papyri and recipe books that nobody was tortured to produce.
The transfer of the object onto Vodou happened in the United States in the early twentieth century, in the period of the American occupation of Haiti from 1915 to 1934, and it was carried by sensational travel writing, pulp fiction and then film. The purpose it served was straightforward: an occupying power benefits from a story in which the occupied population practises something sinister. The doll gave that story a prop.
The result is a religion of several million people known worldwide by an object it does not use, in a caricature built to justify its subjugation. The European poppet, which is the real thing, remains largely unknown.