Why did hillenbrand include both the triumphs of Louie and the ominous background of Japan in the same chapter

The answer is preparing the reader for their collision.

On one side you have Louie's triumphs and the ominous happenings in the world, that is Japan on the other. This technique serves as a hint to their eventual cross and collision. The reader is beginning to expect the the effects of World War to will affect Louie.