The Western allies already secured Italy towards the end of the war. They had a strong presence in the Adriatic and Ionian Seas. The western Allies, particularly the British, had the means to grant countries like Croatia democratic protection so long as they chose democracy like what happened in Italy. But that wasn’t in the plan. Croatia’s strategic position was not appealing enough. The plan was to have the western Allies control Greece, Italy, Egypt while Stalin can drop his Iron curtain at Trieste which would absorb Yugoslavia. Tito wasn’t ousted out of Comintern until a 1948 so in 1945 he was still very much a Stalinist and a lachey.