You forgot to mention:
The Hawaiian Operation was not the primary focus of the war, the goal of the war was to take the Southern Resource Area.
Japan did not have the troops available to take Oahu, the Army only allocated about 10 or 11 Divisions worth of troops for the entire Pacific war, the rest were needed in China.
Japan did not have the shipping to carry troops and supplies to invade Hawaii. Indeed Japan started the war with a shortage of shipping.
Japan had no fleet train to keep the IJN in Hawaiian waters for more than a few days.
Invading Hawaii was impossible for Japan, because they did not have the resources and foolish because it would have lost them the war.
Oahu had the 24th and 25 infantry divisions plus the 34th engineer regiment, all full strength regular army formations in Dec 41'
There was no stronger American army garrison anywhere.