Why does Apollo stop protecting Hector in the Iliad?

In the Iliad, Apollo stops protecting Hector after he has been struck down by Achilles. Zeus, who had previously granted Apollo the authority to shield Hector, decides to withdraw his support to fulfill a prophecy that Achilles would avenge the death of Patroclus. This shift in divine favor highlights the theme of fate versus free will, as even the gods cannot fully intervene against the predetermined destinies of mortals. Thus, Hector's demise becomes inevitable once Apollo's protection is lifted.