What do you think is President Roosevelt's purpose for writing this speech?

Explanation:

He sought to emphasize the historic nature of the events at Pearl Harbor, implicitly urging the American people never to forget the attack and memorialize its date. Notwithstanding, the term "day of infamy" has become widely used by the media to refer to any moment of supreme disgrace or evil.

why does the crew join ahab's quest without hesitation?

it is the background information on the characters and setting explained at the beginning of the story. the exposition will often have information about events that happened before the story began. the exposition is often the very first part of the plot.