As always, read the whole section by Athanasius. But I want to focus on his last thought in it.
Or why, if Christ is, as they say, a man, and not God the Word, is not His worship prevented by the gods they have from passing into the same land where they are? Or why on the contrary does the Word Himself, sojourning here, by His teaching stop their worship and put their deception to shame?
I think it might be easy for us, in our modern Western society, to miss the impact of his point here. Gods were tied to places and to peoples. Athanasius is pointing out that the worship of Christ is spreading across all lands, all places, and all peoples. And the gods who were there before him seem powerless to stop him. Christ is not bound to any place or people. If he’s just a man and not also the divine Logos, how is that possible?