Yahweh continues speaking to the refugees. (See: Isaiah 45:20)
Here the word “them” refers to the refugees from among the nations who worship idols.
Yahweh uses questions to emphasize that he was the one who told them these things would happen. AT: “I will tell you who has shown this from long ago. I will tell you who announced it. It was I, Yahweh.” (See: rc://en/ta/man/translate/figs-rquestion)