The Papacy has long declared the importance of Jerusalem, and Popes were the ones to instigate many of the Crusades. They do this because of how central the city is to the religion

On the other side, because of how vital it is to Islam, a large amount of Caliphs and generals throughout the centuries centered on the city for its religious importance and to solidify regional power.

Both sides viewed controlling the city as the highest holy matter.