The Japanese leadership had come to the conclusion that they needed national self-sufficiency for their growing military aspirations.
They didn’t have the oil and other natural resources in their own territories to make this a reality.
They had two choices: Take it from Russia in the form of Siberian resources, or take it from Western colonies in SE Asia. The first required a lot more Army units than they had. So, they went with taking them from SE Asian colonies.
The Japanese understood that they could not win a prolonged war with America. Their solution was to destroy America’s offensive ability in the Pacific theater and remove Americas will to fight so that they would sue for peace.