Japan was in a tough strategic position (of its own expansionist making), it was basically dependent on American oil during the 1930s, and as it seized land throughout Asia the United States ramped up economic sanctions and export controls targeted at Japan. The United States was hesitant to embargo oil exports to Japan out of a recognition that Japan was so dependent on them, it would have a very high likelihood of bringing Japan to the point of war with the United States. After seizing French Indochina in 1941 the U.S. finally felt that the line had been crossed, and began an embargo on oil exports to Japan.
Japanese war planners essentially felt that this would now necessitate an attack on the Dutch East Indies to acquire their oil reserves. More bellicose elements felt that doing that would essentially require too an attack on the United States, for the reason that the United States had made warnings against attacking the Dutch East Indies. Japan basically was feeling the effects of a vice, it knew even at this point it likely couldn’t win a war with the United States, and the United States and its actions against Japan were curtailing Japan’s ability to grow stronger. It was thus seen that Japan’s only option was to act aggressively, take the Dutch East Indies to secure oil supplies, and then bloody the nose of the United States in order to back it out of East Asia. This would then allow even more Japanese expansion and would end Japanese reliance on Western oil imports.
It’s interesting that Japan likely gravely miscalculated the American public in two different directions. Firstly, it massively overestimated Roosevelt’s political capacity to respond to an invasion of the Dutch East Indies. Roosevelt was basically putting out a serious bluff, because the domestic politics of the United States in 1941 certainly would not have permitted Roosevelt to declare a “pre-emptive war” against the Japanese Empire over the conquest of some Dutch Colonies many thousands of miles away. So the reality is the Japanese could have taken the Dutch East Indies, would likely have not faced a declaration of war from the United States, and could have focused on retrenching its strategic acquisitions.
Long run I think Japan conquered a whole fuck of a lot of shit, and am skeptical it could have held onto that territory long term (I use that term to mean more than say, 20 years in this case), I think it would have been an endless series of Asian wars and drain on Japanese resources and likely eventually lead to an economic collapse and retrenchment from its overseas possessions–in some ways Japan would be looking at trying to build a smaller version of the British Empire with less resources than the British; and the British made a deliberate decision to not put up much fight as its Empire broke away, the Brits realized there was simply no winning that battle and no profit in trying.
But of course the reality is Japan felt it needed to attack Pearl as part of its overall scheme to seize the Dutch East Indies, and its second miscalculation was that a devastating attack at Pearl would sap American resolve and force America to a negotiating table. Japan hoped for some sort of deal in which maybe it makes a few territorial concessions (especially of territories it probably knew it couldn’t hold), in exchange for an end to all sanctions, or even guaranteed access to x barrels of fuel per month–Japan had offered to make territorial withdrawals in the exchange for a cessation of American economic warfare and guarantee of fuel supplies just months before.