Why does Nui have a different settlement history from other Tuvalu islands?

Nui has a distinct settlement history compared to the other islands of Tuvalu because it was heavily settled in prehistoric times by Micronesians from the Gilbert Islands (now Kiribati).1

While the initial settlers of the other islands in the Tuvalu group were primarily of Polynesian origin, arriving from Samoa, Tokelau, and Tonga, the influence of Micronesian migration makes Nui unique within the nation's cultural and historical context.21