I think you should double check it and see if you can find the answer if not come back and ask again
Answer:
they didnt have the neccesary stuff
Explanation:
Because they belived the Manchos Dynasty had lost the Mandate of Heaven
Competition between european countries such as portugal and spain affect overseas exploration and expansion, they didn´t want to go to America, they both wanted to go to Asia, and Africa, trade with asia, get their riches, improve technology and covert people to Christian. Christopher Columbus wanted to go to Asia when he found america, as a result of all that competition, spanish and portuguese established colonies in america.