The main way that the Crusades increased European interest in trade was by exposing them to more goods than they had previously known about trading for.
When the Crusaders spent time in the Middle East, they found that the Arabs and other Muslims had been trading with places farther east. They saw that there were all kinds of new goods that they could get (and money to be made getting them).
Because of this, they became more interested in trading both to get the new goods and to make money.
In addition to fighting during the Crusades, trade was an important component as new goods and ideas were exchanged. They came into contact with empires that were in many ways more advanced than their own. The Arabs taught Europeans about advanced mathematics and the numeral system, in addition to medical principles that had long been forgotten.
Crusaders had to buy their own foods and were introduced to new items that they would bring back with them to Europe. These foods included sherbet, sugar, coffee, fruits, and rice. The introduction of new food items helped increase trade with the East.
Everyday household items were also bought from Muslim traders and included mirrors, textiles, carpets, and sailing compasses. It became obvious that the east was technically more advanced. When these goods were brought West, demand for trade was enhanced. Many of the goods were thought to be exotic in nature and the wealthy felt compelled to buy them. The increased demand for these items sent merchants to the east permanently to establish trade networks. These trade ties led to a regulated currency system that enabled fair trade between the two parties.