It's actually rather unsurprising, given that the Italian army was fundamentally dealing with an insurgency; which is never an easy thing to deal with. In fact, in 1916 Italian forces had disembarked rather easily in Vlora (or Valona, as the Italians called it at the time) and proclaimed an Italian protectorate by 1917. Although Austro-Hungarian forces had rapidly moved south to take Durrës the Albanian front remained fairly stable throughout the war until the autumn of 1918, when the Italian army broke through and advanced as far as Bar in Montenegro. However, after the war's end the Italian army continued to occupy the port of Vlora, leading to the armed response by the unhappy populace.

Counterinsurgencies are particularly tricky for uniformed servicemen to deal with; soldiers are trained to fight against a clearly identifiable foe moving in organized actions, not disgruntled civilians. The only real way to stop a counterinsurgency is with ad-hoc policy designed to convince the populace welcome the occupation (a nearly impossible task in and of itself) and a clear willingness by decision makers to embrace a changing and sometimes nebulous series of long-term goals, with the ultimate if ill-defined objective of making the occupiers seamlessly integrate with the local population. Generally, the easiest way to achieve typical counterinsurgency goals is through a combination of economic incentives and cultural/social reconciliation of occupiers and occupied. The Italian government was not only ill equipped to deal with the latter (as were all imperialist european governments of the time) but was also facing a deep fiscal crisis in the wake of the Great War, making the former goal also fundamentally untenable. In addition, long-term occupations are much more likely to succeed when the local population is unenthusiastic about the local government: Although the Italian army had theoretically arrived to liberate Albania from the Ottoman Turks, there was a growing movement in Albania in favor of self-government, an infinitely preferable option to exchanging one foreign occupation for another. Thus, even if the Albanians in Vlora only had about a thousand militants, the general population was more than happy to aid and abet them.

In all, for an insurgency to be successful it does not have to defeat the occupying force in a military action. Rather, it must make continued occupation untenable; and that's exactly what the Albanian insurgents did. By 1920 army mutinies had broken out in the Italian port of Ancona, convincing the Italian government to withdraw from Valona.