What were d’Annunzio’s politics? I tend to see him as a conduit & summoner of forces rather than having any particular commitment. He was an artist; an antenna receiving, channeling & amplifying what was already present in Europe.
Fiume under his rule had universal sufferage & a mixing of anarchists, socialists, nationalists. It also demanded sex equality. These, along with the theatricality, were all features of fascism. But I think d’Annunzio himself was a channel, not a systematic thinker.