Final answer:
Austria-Hungary struggled in World War I due to internal divisions from nationalism, resulting in revolts and territorial losses. Other contributing factors included economic difficulties and food shortages, exacerbated by the complexities of alliances after the assassination of Archduke Franz Ferdinand.
Step-by-step explanation:
The weakness that caused Austria-Hungary to struggle in World War I was not just due to a single factor, but a combination of issues. The assassination of Austrian Archduke Franz Ferdinand did indeed create a lack of leadership, but it was more the catalyst for the war rather than the reason for their struggles within it. Economic instability, technological inferiority, and insufficient military resources all played a role, but the key factor can be seen as nationalism spurring revolts and loss of territory. Nationalist movements within the Austro-Hungarian Empire weakened the state cohesion, making it difficult for the country to unify its diverse ethnic populations for the war effort.
Adding to these internal problems, the conflict after the assassination saw Austria-Hungary's ally, Germany, urging them into war against Serbia, which brought in other nations due to complex alliances. Austria-Hungary was also challenged by economic problems and shortages similar to those faced by its ally Germany. Food shortages undercut the morale and strength of the military and the civilian population. Factional politics and a divided empire simply could not cope with the demands of modern, industrialized warfare.