Imperialism could have trades occur and more troops. However, the nations being controlled by a bigger nation could start to despise said nation. Plus, the larger nation would often make them convert their way, law enforcement would be quite harsh, and they have less food for themselves.
Answer: When a country is developing and becomes stronger it starts to thrive for power and when a country wants power it starts to take over and expand when a country becomes so large and has so much power that it does not know what to do with it is in the best interest to spread out into a nation of the same empire but ran by different people so that they can maintain the control of their growing nation
