Mussolini made up fascism as he went along. It changed several years before he was deposed and would likely have changed again if he had stayed in power.
To Mussolini, fascism meant he would pursue whatever policies he felt like at the time, and the Italian people would follow him loyally.
Like Hitler did in Germany, Mussolini was grasping for a romanticized revision of national history. It was largely fictitious and designed to stimulate Italian nationalism.
Reading Mussolini's own writings reveal a conflicted and contradictory personality.
Well, Mussolini's "Doctrine of Fascism" speech (from 1935) is the only text of his that completely outlines his view of Fascism, and that is the text that I am following when I refer to Mussolini's Fascism.
The difference between Mussolini and Hitler as far as nationalism goes is that Hitler had this grandiose vision of the German people with the fictitious mythology that you have referred to, whereas Mussolini's nationalism was a brilliant political tool that predated Hitler's rise to power by more than a decade.
Mussolini's Fascism was used to construct the principle of the State as an almost divine entity that renders politics completely obsolete, and for good reason. Because Mussolini was able to speak both to the public's fear of the very real possibility of Socialist control in Italy and at the same time inform them that politics were simply the wrong means to the correct end, he was able to severely weaken his political opponents simply by, as I said, making politics completely obsolete.
This viewpoint that the State was the only entity that mattered and that the contributions of the individual and the people as a whole only matter insofar as they benefit the State made Mussolini able to unite the often-fragmented Italian political sphere (which remains much the same to this day) behind him by eliminating ideological differences.
Mussolini's use of this nationalist tool is probably one of the main reasons that Fascism is still common in Italy today (and led by his granddaughter), whereas the philosophies of Hitler have had more difficulty in Germany after the war.
Another, perhaps unintended, consequence of Mussolini's Fascism was that he had to pander to conservative religious values in order to make the people feel that Socialism would damage their way of life, and so established Vatican City and the Catholic Church as the Italian state religion.
Because of this the Catholic Church was able to survive into the modern age, whereas if the Socialists had been able to seize control in Italy the historical struggle between the State of Italy and the Catholic Church would probably never have been resolved, and Socialist Italy would have driven out the Church itself, resulting in the weakening or complete destruction of the Catholic Church as a major religious power.
