There is an aspect of hiddenness to Scripture. Related to this hiddenness is the concept that prophecy is better understood after the event than before it. That is, its fulfilment clearly relates to the prophecy, but this is much harder to grasp before the event.This could seem to imply that prophecy is not really prophecy if we can only perceive it after it is fulfilled, or worse, that it is not prophecy at all and we just look to random events that may line up with vague ponderings—a Nostradamus approach where cryptic predictions have innumerable confirmations.
This is not really what I am getting at. I think it possible to understand prophecy before the event. And some prophecies are quite clear. Jeremiah clearly stated that Babylon was going to conquer Jerusalem. The Jews would be exiled for 70 years and then return. Daniel was praying near the end of that time asking God about the return (Daniel 2:9). So some prophecy is easy to understand. Nevertheless some prophecies are harder to grasp and some is very difficult to understand.
This may be intentional, God gives words he knows will be difficult to understand. This may relate to us not grasping the issue: for example, at times we relate 2 disparate things because they seem similar to us and we fail to see crucial distinctions. This may be because it addresses issues we have yet to encounter: new inventions, different culture.
Whatever the reason is that we struggle to understand, the reason for God giving elusive prophecies may relate in part to him wanting the prophecy to exist—that is, publicising the foretelling of events—without people knowing exactly what is to come, especially those who oppose God.
So I do not mean that the prophecy is vague and any number of events fulfil it, I mean that an event clearly fulfils it, but all the details of the prophecy become much clearer after we encounter its fulfilment.
An example is Isaiah 53, the 4th of the suffering servant passages (Isaiah 42:1-4; 49:1-6; 50:4-9; 52:13-53:12). Isaiah 53 clearly applies to Jesus, as do all of the suffering servant passages. There has been no other life that fits these verses, and applying them to the nation of Israel fails. Yet who could really understand all that Isaiah 53 was saying before the incarnation of the Messiah. Perhaps there were several interpretations before Jesus, but there is only one after him. And did any one person get it correct before Jesus? Peter tells us that not only did the prophets inquire carefully about the salvation to be offered, but also the angels!
Concerning this salvation, the prophets who prophesied about the grace that was to be yours searched and inquired carefully, inquiring what person or time the Spirit of Christ in them was indicating when he predicted the sufferings of Christ and the subsequent glories. It was revealed to them that they were serving not themselves but you, in the things that have now been announced to you through those who preached the good news to you by the Holy Spirit sent from heaven, things into which angels long to look. (1 Peter 1:10-12)Post fulfilment clarity is not ad hoc, it is more an aha moment.
A potential application of this is that if an event accurately fulfils prophecy then this event may be the intention of the prophecy (or the first event in a duel fulfilment). If an event does not clearly match the prophecy (after it occurs) then perhaps the connection is strained and the prophecy is yet to be fulfilled.