Not P but Moby-Dick (62)

[Mike Jing]

>From Chapter 81:

Is this the creature of whom it was once so triumphantly said—“Canst thou
fill his skin with barbed irons? or his head with fish-spears? The sword of
him that layeth at him cannot hold, the spear, the dart, nor the habergeon:
he esteemeth iron as straw; the arrow cannot make him flee; darts are
counted as stubble; he laugheth at the shaking of a spear!” This the
creature? this he? Oh! that unfulfilments should follow the prophets. For
with the strength of a thousand thighs in his tail, Leviathan had run his
head under the mountains of the sea, to hide him from the Pequod’s
fish-spears!

What exactly does "Oh! that unfulfilments should follow the prophets." mean
here? What would be a more explicit paraphrase?