Trade with Asian countries like China was highly sought after due to silk and spices. Land routes going east (from Europe to Asia) often took a while and had a heavy financial toll on them, plus there were conflicts as well. So many European countries tried to find various shortcuts to bypass these problems. The thinking was that they knew the world was round, so eventually they would reach Asia even if they went westward. The problem they didn't foresee was that North and South America was in the way. Though cultures such as the Vikings already knew about the Americas along with the Native Americans of course as well.