The first motive of the Crusade was to liberate the Holy Land for Christians, as that was supposed to bring about the return of Christ and the Last Judgment. Europe in the Middle Ages was a violent place and many blamed the violence and disease on the devil. By bringing about the Return of Christ, many Christian leaders thought that they were fulfilling the prophecies found in Revelation. Also, the Pope wished for Christians to stop fighting each other in wars against kingdoms and to instead wage war against Muslims, who were a constant threat to Italy and Southern Europe.
Economically, the Church made a great deal of money on relics, and the Holy Land had many of them. Relics also inspired the illiterate masses to be more fervent in their worship and their tithes. The Church hoped to bring back relics from the Holy Land in order to kindle more religious devotion in the masses and to encourage more money going to the Vatican.
Most secular leaders derived their power from the Vatican so many sent troops or went themselves to fight in the Holy Land. Many also saw fighting in the Holy Land as a way to cleanse oneself from sin and to ensure a place in Heaven. Many knights and soldiers saw the possibility of loot in the Holy Land as well. While the Crusade was meant for only knights and rulers, many serfs went there in search of salvation by fighting the Muslims.