While it's obvious that they suffered much the same immediate post-war problems - inflation, trouble shifting their economies to function in the post-war world, burgeoning class struggle, nationalist revanchism, fractured coalition governments, severe cultural anxieties etc. I'm struggling to understand why, when issues such as inflation were so much more destructive in Germany it was Italy that fell to dictatorship first, while Weimar democracy survived, albeit in a fairly battered state at times, for almost a decade more.
I have attempted to answer a similar question, albeit coming from a different angle - I don't think it is possible to establish a clear causation pattern for the affirmation of Fascism; and therefore it becomes somewhat insidious to try to explain why it occurred in certain countries and not in others, and when it did.
We can follow its trajectory, and look back for the origin of certain characters of it. In this sense, we see that there are analogues with the German political evolution, but it's difficult to make any stronger assertions on the matter.
As a general note - and you correctly point out many of those elements yourself - it's worth remembering that the evolution of Italian Fascism into a dictatorial regime was slower and more gradual than a proper "fall". More of a bumpy slide along a hill's side.
It took two years to end the first period of "constitutional" government, with the introduction of the new electoral law and the murder of Giacomo Matteotti - and around three more years to enter the stage of proper formation of a Regime.
The transition into Fascism was therefore much less of a neatly divided separation between two different systems that it may appear to us if we compare Fascism with the pre-exisiting liberal system (in fact stressing the elements of continuity with the previous liberal system has been a research direction alternative to the more traditional one since the 1960s - see, for instance R. Vivarelli Il fallimento del liberalismo)
Perhaps more relevant than the elements of objective continuity - which are more or less bound to exist, given how Fascism developed within the Italian social, economical and political system - it's worth pointing out that there were many elements of perceived continuity. That is, for many portions of the political world, of the establishment, of the population, the affirmation of Fascism was neither a fall nor a bumpy ride along a slope - it was more or less one of the many episodes of reincorporation of social, political and economical tensions within the liberal system. Their realization of the new character of Fascism usually, if at all, came later along the way, when they were able to see the hill top from a distance.
Edit: I am not sure my answer can indeed provide much clarity on the matter - feel free to ask for more if you have doubts of any sort.