The gods and goddesses of ancient Greek mythology regularly intervene throughout the Iliad. They get involved at key points, invariably driving the action forward. In doing so, they show themselves to be devious, manipulative, and generally indifferent to human suffering. To the gods, mortals are little more than pawns on a gigantic chess board to be moved around at will.
This attitude towards human life shouldn’t surprise us in the slightest, given that it was the gods who were responsible for the outbreak of the Trojan War in the first place. Let us not forget that it was the goddess Aphrodite who started the whole conflict by awarding the Trojan prince Paris the prize of Helen after he judged Aphrodite to be the fairest goddess of them all. As Helen was already married, this constituted an insult to her husband Menelaus, whose honor the Greeks sought to restore. Hence, the Trojan War.
Ever since then, the gods and goddesses have been intervening regularly in the Trojan War, invariably stretching out the conflict, thus causing more death, suffering, and bloodshed. In book 2, when the Greeks dash to their ships after Agamemnon tells them that the war is over and that they’re going home, it’s the goddess Athena who inspires Odysseus to call them back.
Had the Greeks left there and then, it would’ve saved a lot of lives. But according to the divine plan, Troy must fall, and that means that the Greeks need to stay put until they’ve got the job done. Here as elsewhere in the poem, the will of the gods is all-important, certainly more important than the death and suffering of mere mortals.