It is true that the post-war Italian state and society never truly performed a thorough self-examination regarding the causes and consequences of Italian Fascism. This process of self-examination, or lack thereof, would be one of the defining subtexts of the political conversation in the First Republic.

A powerful contributing factor was mere convenience and inertia: the Italian rebuilding process had begun two full years before serious plans for the post-war order were drafted, allowing bad habits (read, "Fascist Habits") to be subject to a hurried and opportunistic review rather than a thorough examination under the watch of the international diplomatic community or indeed a functioning national press or other manifestation of civil society. Indeed, Italy had been the first Axis state to surrender, and while the American State Department and War Department were aware of the possible consequences of using Italian resources and material for the war effort, they made a pragmatic decision: As early as the winter of 1943-1944 the US authorities adopted a policy of outright industrial rehabilitation. Italy's limited but conveniently located strategic resources were aggregated to the American war effort in opposition to the Wehrmacht, which by then occupied half the peninsula in the flimsy pretext of defending Mussolini's hapless puppet-government in Salò. This meant that in spite of the unconditional surrender demanded and obtained of the King's rump state based in Brindisi in 1943, a process of rehabilitation and legitimization of some fortunate (and fortuitous) members of the political and economic leadership already began occurring while the war was underway. Italy therefore spent the last two years of the war as a battleground, rather than as a belligerent. With "The Enemy" identified as the occupying German forces, the convenience in keeping the existing Italian political administration intact allowed many fascist public officials and fascist-tied business leaders to keep their places of prominence.

As the war progressed and tensions within the Allies began to surface, the lack of actual Soviet troops having entered Italy (save for an attempted Yugoslav occupation of Triest which was not strictly speaking Soviet and was nonetheless rapidly expelled) and the deteriorating situation in Germany meant that it was also very convenient for the United States to lump Italy along with France and Britain in the category of nations to help back on their feet and place in a condition to at least partially fend for themselves should Russian tanks breach the Iron Curtain. Even Italy's forced de-armament, imposed by the peace treaty with the Allies, was ignored upon the country's adherence to NATO. Italy, it would seem, had regained the good graces of the western international community.

But if the ongoing conflicts had dragged Italian institutions along with them, not allowing for a time when serious anti-fascist rehabilitation could occur, it is even more important to stress that there was also no internal push to ask difficult questions of the fascists experience either. The Constituent Assembly, that is to say the legislature in session between 1946 and 1948, collected politicians that on the whole certainly had no sympathetic feelings towards fascism. However, the fascist control over Italy was never total, and the individual experiences of the members of the constituent assembly were very different. Some, especially the Socialists and Communists, had recently been released from political prisons. Some had been leaders of the armed resistance. Others had returned from foreign exile. But others still were returning from having fled from war more than the explicit displeasure of the fascists (this was the case of Amintore Fanfani, an influential parliamentarian and future President of the Chamber of Deputies who had enjoyed a successful university career before waiting out the war in Switzerland). Others still had suffered fascist rule in a relatively benign manner, with figures like future political kingpin Giulio Andreotti going from catholic-aligned activist newspaper editor to mere librarian, certainly a professional downgrade but hardly a tragedy.

Thus experiences under fascism were very different for the various members the constituent assembly, and similarly differing were visions for the future of the country. Indeed, these differing visions would remain largely irreconcilable until the 1970s. The divisions can be in great part traced past the eclectic composition of the Constituent Assembly to the situation on the ground in the immediate post-war governance of Italy, where law and order was nebulously split between the the allied command, the royalist government, whatever local government still existed across towns and provinces, and antifascist militias. All these players exerted authority in various overlapping spheres of influence which crossed social, geographic, and institutional lines. The situation was further confused by the fact that the Italian Communist Party and the Italian Socialist party were participants in the King's government, but although many of the various militias were more or less nominally affiliated to these parties, ultimate authority was nonetheless in the hands of the leaders on the ground. This created an underlying uneasiness tied to armed left-wing revolts precipitating some sort of coup (be it expressly desired by the Communist and Socialist leadership or not) manifesting in the considerations of conservative political leaders. After all, by the war's closing acts armed partizan militias (or Partigiani, in Italian) had successfully opposed and expelled the authorities recognized by the Republic of Salò in various major cities, and achieved surprising levels of organization and discipline. There was a sentiment, especially among the more pragmatic in the conservative ranks, that in the face of such a threatening phenomenon it would be best to avoid unnecessary shocks to the institutional order.

So while the national vision elaborated by the fascists had been smashed in the dual fire of civil war and foreign invasion, two competing visions would rise from these ashes: Catholic and Communist. While the reconstruction of the country had already begun without a purge of fascism from Italian institutions, those residues of fascism would continue to be much more tolerated by the Christian Democracy party than the Communists or Socialists, who would instead turn their struggles against Fascist oppression into the defining narrative of their collective history (however, I would also point out as an aside that many Christian Democrats were also proud of their antifascist activism, albeit less loudly than their rivals to the left). We can speculate that if the partizans had propped up a communist government perhaps there would have been a comprehensive purge of fascists, or perhaps there would have been a wholesome embrace of the fascist social skeleton to lay the foundation of a Soviet Socialist Republic. We cannot know, because it did not happen. Rather, after an initial yearlong period of collaboration the Italian Communist Party and the Christian Democracy party would place themselves at the antipodes of the political spectrum, and the Christian Democrats would not relinquish the Prime Minister's post, or indeed effective control of the government, until 1983. The haphazard model of state construction very nearly developed on the fly as the Second World War came to a close would become the line followed by the Italian government thereafter, for decades reliant on foreign legitimization and especially prone to a very Italian train of thought whereby "everything will have to change for things to stay the same."

If you'd like to read more, there's the old Italy and the Allies by Norman Kogan, published in 1956. A more recent book with a more holistic examination of post-war Europe is Cold War Europe: The Politics of a Contested Continent by Mark Gilbert, published in 2014. Paul Ginsborg's 2003 A History of Contemporary Italy: Society and Politics, 1943-1988 is another, Italy-specific, resource you might want to look at (however I'm not entirely sympathetic to Ginsborg's internal political analyses).