Why does Priam take Hermes calling him “father” as “an endorsement and blessing”? (161)

When Hermes tells Priam to prepare, as they are approaching the Greek camp, Priam takes heart from Hermes’ presence, and from the fact that earlier, he called Priam “father,” something which acts as an endorsement and a blessing coming from a god. Although Hermes never reveals who sent him, it's safe to assume that the gods are on Priam's side in this endeavor, even if they won't interfere. This reveals that even the gods are shocked and disturbed by Achilles' actions, but also that the gods are limited by how much they can interfere in human affairs. Hermes can give Priam a boost, but he can't rescue Achilles for him. He can give them his blessing, but not an assurance that nothing will happen to them. He can open the doors of the Greek camp, but can't lead them through. As Iris mentioned earlier, the most important elements of this plan will ultimately be left up to chance.