They were various motives that made empires seek to expand their rule over other countries and/or territories. Some reasons include economic, exploratory, ethnocentric, political, and religious motives.
There was a lot of reason for why imperialism had started. It dawns back even before the romans. But the most common sly known reason for imperialism is expanding the territory or ones country or territory. Like for example a lot of countries in Europe way back attempted to take all of Africa.
