The Aleutians were utterly worthless, and one of the tragedies of the war is that we spent so many lives and resources pointlessly recapturing them - it actually prolonged the war.
Previously, the aleuts were not consider a strategic asset. What good were they? Too far a way and too difficult to support in a cold weather environment. We did however, use them to make 2 bombing runs into northern Japan, demostrating their long term usefulness. The amount of dollars spent in the Aleuts and all of Alaska to this day continue to demostrate their value.
If the japanese had concentrated on the aleuts and been able to take mainland alaska, she would have been in a far better place for attacks up and down the Pacific Coast, then we would have been for attacks into Japan.
utterly worthless? Hardly. We wouldn't have spent so many men and dollars retaking them or the great numbers of dollars that have been spent their since.
What a miserable campaign that was.
I have no idea what the specific thought process was of those making the decisions back then, but I'm guessing that it was plan-B.