Why did nationalist movements have an influential force in Italy?

Because Italy, after the end of the First World War, considered itself an offended state. Despite the fact that back in 1915 she joined the military-political bloc of the Entente, which became the winner in the war, the Italians ended up with practically nothing in terms of territorial acquisitions. Therefore, strong anti-French and anti-English sentiments grew among Italian society at that time, which led to revanchist sentiments, the growth of Italian nationalism and the emergence of a fascist movement.