Final answer:
Venice encouraged the Crusaders to attack Constantinople to weaken a trading rival, taking advantage of the Fourth Crusade to serve its own economic interests, which led to the catastrophic sack of Constantinople in 1204.
Step-by-step explanation:
The reason Venice urged crusaders to attack Constantinople was primarily to weaken a trading rival. By the time of the Fourth Crusade, Venice saw a strategic opportunity to redirect the Crusaders against Constantinople. When the Venetian leadership provided ships to the crusaders, they first asked them to attack the port city of Zara, a Christian city but also Venice's rival.
Constantinople, a city rich in history and wealth, was a long-standing trading power and a commercial threat to Venice's ambitions in the region. The sack of Constantinople in 1204 by the Fourth Crusade was catastrophic for the Byzantine Empire, leaving lasting resentment and contributing to the rift between Eastern Orthodox and Roman Catholic Christianity.