When the Christians traveled to the Holy Land to reclaim it, they were introduced to new spices and food that they had never seen before. They took it back to their home. So of course the people that lived in the Middle East wanted something in return. So the trading begun.
I believe that they did help in establishing trading ties becuase a lot of people from Europe acquired a taste for things only found in the Middle East. Many spices that had never been tasted in Europe, or were considered a luxury, became commonplace and demanded by the majority of European citizens.
I believe because of all the people from Europe going over to the Middle East and fighting the Crusades opened up the opportunity for merchants to benefit from this, I believe that because of the Crusades many trade routes opened up between Europe and the Middle East that still exist today.
The Crusades were successful at establishing trading ties between Europe and the Middle East. There was an ebb and flow of trade between Europe and the Middle East during the Byzantine-Seljuk wars which took place around the 10th century AD. In addition to trade, political relationships were formed between Christians and Muslims.
As wars tend to do, the Crusades led to animosity between
Muslims and Christians. Of course, not all Crusades targeted the Holy Land;
some were launched against Christian denominations. It is also true that in
some places, such as Spain, Muslims and Christians met in harmony, at least for
a time, and that some Christians and Muslims became trading partners. However, the
overall effect of the Crusades was to promote ill feeling.