Question

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

Answer 1

The crusades helped drive some of the seljuk Turks out of the area, but (according to Wikapedia) "It also opened up byzantium to Latin aggression which was not always dedicated to Byzantium's enemies"

Also, the Fourth crusade (made up of Latin crusaders) sacked Byzantium and greatly reduced power in the empire.

Answer 2

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