Achilles didn’t exactly save the Greeks. He is no doubt the hero of the Trojan War as portrayed in the Iliad. Though the greatest of the warriors, the idea of the Trojan horse was Odysseus’ brainchild. It is primarily his wise counsel, as guided by the goddess Athena, his strategies that secured the victory.
As to everybody getting killed during his return except Odysseus himself, it is clearly a symbolic story that further highlights the wisdom of the Greek hero. What is being depicted in the epic and its aftermath is the end of the Bronze Age. It is just the same as happened in the Mahabharata War that saw very few survivors, just about 18. That is not a verdict on the leaders and warriors but simply a sign that the Age was changing and the gods who were protecting their worshippers were withdrawing themselves and hence some of the greatest warriors were killed or destroyed, including King Agamemnon and Priam. It was a large-scale destruction on both sides.
Affectionately
Alok Da
