Just read through a couple of brief references, and the whole thing started with a decision in 1942 that the US would need the small airstrip on Palau.
Amazingly by the time they decided to invade they didn't need that airstrip because aircraft had been improved substantially.
The whole point was it was a glorious battle with a lot of bravery, and it didn't have to be fought ~ just another island that probably should have been skipped over.
from what I understood we were destroying the airfield so Japanese wouldn't use it to attack our forces during the other island attacks.