The reason and cause of the crusades was a war between Christians and Moslems which centered around the city of Jerusalem and the Holy places of Palestine. The City of Jerusalem held a Holy significance to the Christian religion. Two major effects of the Crusades were that the kings' authority increased and the Europeans learned about new things from the Muslims they encountered. During the Crusades, the kings increased taxes to fund the cause. Many peasants also left their land to fight, and when they died, the land went to the king.
One of the reasons was the blocked transportation routes, another was they were giving so many materials to the army to win they put aside their other business to focus on that
