Before Europeans started searching for a sea route to the Orient, merchants from Europe took land routes to the Orient (Silk Road) for trade but around the 14 to 16th century, the empires controlling some of the areas they had to pass started demanding heavy tolls from the merchants to pass their empire. The Europeans were forced to find another route to the East.
Another reason for the search of a sea route was because they wanted to increase their trade profit. Finding a sea route will help cut out the middlemen that were delivering goods to Europe at high price. A sea route was needed so they could transport more goods at cheaper prices.