Why did Palau become part of the United Nations Trust Territory of the Pacific Islands?

Palau became part of the United Nations Trust Territory of the Pacific Islands in 1947 following the defeat of Japan in World War II.12

During the war, the United States secured the islands from Japanese control through its Pacific campaign. After the war, the United Nations established the trusteeship system, which was designed to ensure that territories taken from defeated powers were not simply annexed by the victors but were instead administered under international supervision to guide them toward self-government or independence. Consequently, the United States assumed responsibility for the administration of the islands, including Palau, under this UN mandate.132