Why did the Fourth Crusade sack Constantinople instead of attacking Egypt?

The diversion of the Fourth Crusade from its original goal of attacking Egypt to the sack of Constantinople in 1204 was primarily driven by financial desperation and political opportunism rather than religious intent.12

The crusaders had contracted with Venice for a fleet and provisions they could not afford, leaving them with a massive debt. To address this, the Venetian leader Enrico Dandolo persuaded the crusaders to capture the Christian city of Zadar to suspend their payments.32

Subsequently, the exiled Byzantine prince Alexius IV Angelus offered the crusaders immense wealth, military support for their campaign in Egypt, and the submission of the Byzantine church to Rome if they helped him reclaim his throne. The crusaders accepted this proposal to resolve their financial crisis. However, once installed, Alexius IV could not fulfill his promises, leading to a palace coup and his eventual death. Cheated of their reward and facing hostility, the crusaders turned their military force against Constantinople, resulting in the city's brutal sack.421