Final answer:
The Templars and Hospitallers foresaw difficulties in securing Jerusalem due to a lack of European settlers, challenging relations with local populations, the emergence of powerful Islamic states, and shifting European priorities.
Step-by-step explanation:
The Templars and Hospitallers, among others, believed the crusaders would not be able to secure Jerusalem long-term for several reasons. The Christian knights, despite their initial successes and fervent religious motivations, faced significant challenges. The First Crusade led to the capture of Jerusalem and the massacre of its Muslim and Jewish inhabitants, an act that damaged relations with local populations. Furthermore, the influx of European settlers was insufficient to maintain a robust defensive presence, leaving the Crusader States vulnerable. The arrival of the crusaders was met with mixed reactions from the local Eastern Christian and Jewish populations, and the overall lack of cooperation weakened their position. Over time, the political and military landscape in the Middle East changed with the rise of powerful Islamic states such as the Mamluk and Ottoman empires, making the Christian hold on Jerusalem increasingly untenable. Internal conflicts among the crusaders and the priorities of European monarchs back home also played a role in the ultimate failure to secure Jerusalem. Strategic fortifications like the Krak des Chevaliers were constructed to bolster defense, but the scarcity of European reinforcements and the shifting focus of European powers towards internal nation-building decreased military support for the Crusader States.