Why Italy could not make the Mediterranean Mare Nostrum

Why could Italy not achieve Mussolini's goal of Mare Nostrum?

Britain and France remained powerful Mediterranean competitors, and the sea was too strategically valuable for one state to monopolize without first controlling its coasts and eliminating rivals.

Mare Nostrum was achievable for Rome only after Roman power controlled the Mediterranean coastline and eliminated peer competitors inside the basin. In the interwar era, Britain and France both possessed major interests and naval forces there. Britain enjoyed de facto predominance during parts of the nineteenth century, but even that fell short of exclusive Roman-style control. The sea was too valuable as an international route for other powers to accept an Italian monopoly.