The most likely reason why Emperor Hirohito remained head of state when military leaders took power in Japan would be: Military leaders wanted to maintain the illusion of a single powerful leader.
At that time, the military leaders only need the emperor as a front puppet that maintain the stability in society. This would take their attention away from the decisions that were made by military leaders regarding Japanese invasion to other countries.
Lewis and Clark's team mapped uncharted land, rivers, and mountains. They brought back journals filled with information about the Native American tribes. They also brought back scientific notes about plants and animals they'd never seen before.
