Why does Telemachus think Odysseus is a God?

Telemachus is initially surprised by the stranger's ability to change his appearance and mimic the voices of his father and other chiefs, leading him to believe that the stranger must be a god. However, when the stranger reveals himself to be his father, Ulysses, Telemachus quickly realizes that the transformation was the work of the goddess Minerva, and not a sign of divine power. He does not attribute any divine power to the stranger, instead he continues to refer to the stranger as Ulysses and not a god. Laertes also confirms this when he remarks that he wishes he was still the man he was when he ruled among the Cephallenians, and that he would have been able to help Telemachus against the suitors if he had been in the house with his armor on. Ulysses then further confirms this when he explains that it was the Phaeacians who brought him to Ithaca, and that it was Minerva who had enabled him to change his appearance. This is further reinforced when Theoclymenus interprets the hawk's presence as a sign of good fortune for Telemachus.

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Telemachus answered, “Antinous, do not chide with me, but, god willing, I will be chief too if I can. Is this the worst fate you can think of for me? It is no bad thing to be a chief, for it brings both riches and honour. Still, now that Ulysses is dead there are many great men in Ithaca both old and young, and some other may take the lead among them; nevertheless I will be chief in my own house, and will rule those whom Ulysses has won for me.”

Then Eurymachus, son of Polybus, answered, “It rests with heaven to decide who shall be chief among us, but you shall be master in your own house and over your own possessions; no one while there is a man in Ithaca shall do you violence nor rob you. And now, my good fellow, I want to know about this stranger. What country does he come from? Of what family is he, and where is his estate? Has he brought you news about the return of your father, or was he on business of his own? He seemed a well to do man, but he hurried off so suddenly that he was gone in a moment before we could get to know him.”

“My father is dead and gone,” answered Telemachus, “and even if some rumour reaches me I put no more faith in it now. My mother does indeed sometimes send for a soothsayer and question him, but I give his prophecyings no heed. As for the stranger, he was Mentes, son of Anchialus, chief of the Taphians, an old friend of my father’s.” But in his heart he knew that it had been the goddess.