The most accurate explanation for why enslaving the Indigenous peoples of the Americas was largely unsuccessful in filling the need for labor on plantations is: European colonizers’ cruelty, as well as the spread of disease, meant that many Indigenous people died. As a result, there were not enough people left for colonizers to enslave.
This response captures the impact of both direct violence and the devastating effects of diseases brought by Europeans, which significantly reduced the Indigenous population, making it difficult for colonizers to rely on them for plantation labor.