Why would Richard I have struggled to hold Jerusalem after capturing it?

Richard I recognized that he would struggle to hold Jerusalem because he lacked control of the surrounding hinterland. Although he advanced on the city twice during the Third Crusade, he ultimately decided against laying siege to it, concluding that even if he were successful in capturing the city, he would be unable to maintain control of it for long without securing the interior territories.12

This tactical assessment was based on the strategic realities of the campaign, where the Crusaders' presence was largely restricted to a coastal strip. While Richard’s decision was considered sound from a military perspective, it was deeply unpopular among his troops, who had hoped to reclaim the holy city.312