I'd like to draw a comparison between prophecy and the progress of science. People often ask, what did OT prophets know? For instance, Isaiah prophesied about a Davidic messiah, but did he know who that would be?
I've read it said that Kepler's three laws of planetary motion anticipate Newton's inverse square law. I've also read it said that Mach and Poincaré anticipate Relativity.
Now, in one sense that's anachronistic. That's a retrospective judgement. In light of subsequent developments, we might see how their work led to the work of Newton and Einstein. But of course, they didn't have the benefit of hindsight. Although we're in a position to recognize how their work contributed to later developments, their own perspective wasn't prospective.
But in another sense, this isn't just reading the future back into the past. Newton and Einstein really did build on the work of their predecessors. That's what made the breakthroughs of Newton and Einstein possible. Although Kepler, Mach, and Poincaré couldn't foresee how Newton and Einstein would exploit their insights, there is a genuine trajectory. We can retrace the pathway.
Now, this is just an analogy. I'd say the relation between prophecy and fulfillment is stronger than that. But even if, for the sake of argument, it was weaker (see above), there's a real link between what went before and what happened afterwards. To the extent, moreover, that the detailed circumstances of the outcome were unexpected, that makes it all the more striking.