Why was the fourth crusade such a disaster?

The Fourth Crusade, launched in 1202, was a disaster primarily due to its diversion from the original goal of reclaiming Jerusalem. Instead of heading to the Holy Land, the crusaders were manipulated into attacking the Christian city of Zara and later Constantinople, driven by Venetian interests and financial debts. This betrayal deepened the schism between the Eastern Orthodox and Roman Catholic Churches, undermining the unity needed for a successful crusade. Ultimately, the Fourth Crusade not only failed to achieve its religious objectives but also weakened Christendom and exacerbated tensions between Christians and Muslims.