Cause the bigger the population the more seats in the house you have
it is considered an insulator
As the United States President, it was his job to save American lives. He figured if he used the A-bombs against Japan, he'd save more American lives (because they wouldn't have to risk land invasion).
The goal of Pikes expedition was to find the source of the Red River whereas the goal of Lewis and Clark's journey was to find any unknown Territory
Hope this helps!