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Something missing from the map is that sailing the open sea was very risky business in the ancient world. Both Rome and Carthage lost entire fleets to bad weather crossing the comparatively short stretch between Sicily and Tunisia. The ships of the Trojan War period were probably less advanced, though not by much, and would have pulled a shallow draft at least as shallow as the biremes and triremes that came to dominate the Mediterranean centuries later.
As such, this meant the Phoenicians and Trojans, when departing into their respective exiles, would have had to keep the shore in view, sometimes while sailing through unfriendly waters. While ships of the period did have sails to help power them, the speed and maneuverability of a ship was almost completely dependent on the strength of the oarsmen driving her.
In leaving Carthage for Italy, the Trojans would have had to sail across open sea, faced with the threat of pirates and bad weather, and nothing more than the strength of their own backs to get them through it. It kind of makes you wonder that any of them would have left.