Final answer:
Napoleon put his brother on the Spanish throne to maintain control, expand French influence, and consolidate power within his family.
Step-by-step explanation:
Napoleon installed his brother, Joseph Bonaparte, as the king of Spain for several reasons. One reason was to ensure that Spain remained under French control and to prevent it from aligning with Britain. Another reason was to further extend French influence and dominance throughout Europe. Additionally, by placing his brother on the Spanish throne, Napoleon aimed to strengthen his own family's power and control over various territories.