Question

In what way did the Christian Crusades contribute to the decline of the Byzantine Empire?

Financing the Crusades proved to be an impossible burden for the Byzantine treasury.

Latin Crusaders turned against the Byzantines, leading to the loss of much territory.

The Byzantine army lost many of its leading knights when they left to fight in the Crusades.

Nations that were not joining the Crusades attacked Byzantium when it was occupied in the east.

Answer 1

Latin Crusaders turned against the Byzantines, leading to the loss of much territory.
Another cause was the Seljuk Turks that frequently attacked Byzantine Outposts and settlements.