Why did so many people take part in the crusades?

The Roman Church was a powerful force behind the Crusades. The promise of both earthly and heavenly rewards lured many into taking the Crusader's vow. Church leaders guaranteed the protection of the family and property of the Crusader while he was away. Criminals and debtors undertaking the "holy" cause received pardons. In fact, the popes proclaimed that participation in the Crusades was a substitute for penance. Hardened sinners were told they could earn forgiveness of sins by joining one of these campaigns. Furthermore, the Roman church assured the Crusaders that anyone who died while on a Crusade would be granted eternal life. The Roman church manipulated the the credulous people by giving them false assurance.