By the time of his death, most of Italy had already been liberated by the Allies with the help of the partisans, and it was pretty much under occupation; those who associated with him either faded into obscurity - many were never tried - or simply found a new political alignment. After the war, both the Fascist Party and and its eventual reformation were outlawed, but most of its adherents simply kept quiet... a few would actually go on to found a number of far-right parties which were Fascist in all but name.
Which system carried on Italy after fascism?
Italy was a monarchy - actually, it still was one for the whole duration of the regime (with Mussolini being, at least technically, a Prime Minister) - but support for the House of Savoy had dwindled due to the war and Victor Emmanuel's accommodating stance towards Fascism. This lead the new King, Umberto II, to indict a much discussed referendum in which many alleged irregularities as well as episodes of deliberate suppression of pro-monarchic activity occurred.