Why was a fourth crusade called by pope innocent iii?

The Fourth Crusade was called by Pope Innocent III in 1198 primarily to reclaim the Holy Land from Muslim control after the failure of previous Crusades. Innocent aimed to unite Christendom and restore Christian access to Jerusalem, which had been lost in 1187. However, the expedition was diverted due to political and financial motivations, ultimately leading to the sack of Constantinople in 1204 instead of the intended goal. This diversion significantly impacted relations between the Western and Eastern Christian churches.