Why have nation-states been more successful, as political units, in modern world history then multinational empires have been?

Empires had a meaning when land was the prime wealth of a state. The more the land, the more the peoples, the more profitable the taxation. As of the Renaissance however, the bourgeoisie had begun to prove that, better than land possession, trade and exchanges were the key to a wealthy nation. Because multinational empires had become antihistorical.

Is there a passage that comes with this question or should i know this right off the bat, because if it is, i probably have short term memory loss or college is too stressful

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