Answer:
To help you out this is what I think the answer is They believed that if they found a new and faster trade route it would be cheaper to get the goods. In 1488, King John II of Portugal sent a man by the name of Bartholomeu Dias to explore the southernmost part of Africa. this is for the first part of your question, for your second one this is what the answer is they wanted to be the ones that where the ones who wanted the most land. they didnt want anyone else to have something they didn't.
Explanation:
Watch Pirates of the Caribbean On a strangers tide then you see what i mean.
