Why animals?
This is the first book ever to win a Caldecott Medal, and it definitely shows its age. It is very wordy. It's just a bunch of passages from the Bible that depict animals, or even mention animals in passing or in metaphor. Most of them are illustrated by pictures of the animals. Some of the more interesting ones are "behemoth," which is apparently a hippopotamus, "leviathan", which is some kind of bizarre sea serpent, Jonah and the "great fish", which is clearly a baleen whale, and Jesus's saying that "the foxes have holes" apparently warrants a depiction of foxes. There's a picture of Jesus riding what is obviously a donkey, although it is described as a "colt" in the text. Also included is the cock which crows after Peter has denied Jesus three times.
But not, for example, the she-bears that maul children for mocking Elisha, or the plague of locusts. Only good animals. The nice animals are depicted here. That's it. Nothing really that interesting. There's no discernible moral to it. There's no obvious reason that they chose to illustrate animals. There's no point they seem to be making. It's just weird.