The japs were viciously evil, but they were not stupid...
Almost 100% of all their war-fighting raw natural resources had to be imported...
They focused on our fleet because there were no long columns of supply ships bringing required raw war-fighting resources to the American mainland...
The few that did exist were being handled by the German U-Boats quite handily as they came from South America through the Caribbean to the U.S.
The U.S., way back then, had massive homeland resources of raw materials, the planet's largest manufacturing base, and hard-working patriots who loved their country...
All of these have been deliberately eliminated in the past 50 years...
Oh yes they were stupid. They had superb submarines and torpedoes but did not use them in any meaningful way to interdict supplies flowing from the west coast to Australia, or from Britain east through the Indian Ocean to Australia.