While an attach on Pearl Harbor had been wargamed several times, the US expected the main Japanese thrust to be at the Philippines, Malaya, and the Dutch East Indies, which in fact was what happened.
The Pearl Harbor strike was a one shot given the distance involved. There was opposition to it in the Imperial Japanese Navy. Yammamoto lucked out in having two brilliant officers, Fuchida and Genda, to plan and lead the attack. Under other circumstances it might not have worked.
Which is one of the key reasons why there were not troop transports sent with that task force.
Many records of the pre-Pearl Harbor warnings and responses were destroyed, so we'll never know exactly who expected what to happen. And those who defend the Roosevelt administration claim that none of the Japanese messages pointing to Pearl Harbor as their target were decoded on-time.
But many records did survive, along with later testimony which adds up to dozens of warnings from spies, diplomats and foreign military (British & Dutch) plus decoded messages.
Indeed, there were enough warnings, along with the fact that the US Navy had been actually practicing the attack for years, that we have to wonder: were these warnings actually overlooked, or were they deliberately ignored, and if so why?
I think the answer is: they were deliberately ignored, and the obvious reason is, for much much larger strategic purposes.