<span>1.The Chinese did not have any more uses for a navy.
2.The voyages were becoming to expensive.
3.They wanted to divert their attention to stopping the Mongolians.
4.The Chinese began to adopt a policy of isolationism and did not want to interact with anyone.</span>https://answers.yahoo.com/question/index?qid=20130423165801AABEmGv
By selling Louisiana to the U.S. in 1803, Napoleon obviated the need to defend it against the British, and he may have hoped that the need of the U.S. to defend the territory (against the British) might have brought America back to its alliance with France.
Hope this helps
They did cause they were terrible people who’s land and resource were failing
Imperalism by definition is the policy of expanding your countries power through military or diplomatic means. And expanding your country to another continent, with many resources untapped and people of inferior technology means you could easily conquer and expand
