Why did the Polynesians choose to migate?

Despite predominant easterly winds in the subtropical Pacific, Polynesian navigational skills and the aid of cyclic or seasonal changes in the winds and currents enabled dispersal from the western Pacific to islands as distant as Easter Island and Hawaii.

one of the reason is that they had forbidden terrain and poor conditions for farming

nuclear fission produces the atomic bomb, a weapon of mass destruction that uses power released by the splitting of atomic nuclei the fighting in iwo jima and okinawa affected the allies' pacific strategy because truman decided to drop the atomic bomb on mainland japan.