What was the reason for an occupation of the first group of americans to settle in hawaii?

The Kingdom of Hawaii was prosperous and important for its agriculture and strategic location in the Pacific. American immigration began almost immediately after European contact, led by Protestant missionaries. American methods of plantation farming for sugar required extensive labor. Several waves of permanent immigrants came from Japan, China and the Philippines. Meanwhile, the native population began to decline steadily from disease from 300,000 in the 1770s to 60,000 in the 1850s to 24,000 in 1920.[1] Americans within the kingdom government rewrote the constitution, severely curtailing the power of King "David" Kalākaua, and the rights of Native Hawaiians and Asian citizens to vote. Queen Liliuokalani attempted to re-store the old royal powers in 1893 and was overthrown by businessmen with help from the US military. The Republic of Hawaii was formed for a short time until the government agreed to join the US in 1898 as the Territory of Hawaii. In 1959 the islands became the state of Hawaii of the United States.