Alot, if not most of the current olympical diciplines have some military significance. Like the marathon being for long distance correspondence, wrestling to train hand to hand combat and the pole vault (im guessing) for sieges. But what I cant Imagine, is what use the triple jump might have had. Clearing a distance with a skip and a jump doesnt seem all that useful to me.
Did it have any use at all?
I can't comment on the triple jump specifically, but I think you're overstating the military significance of the other events. Chariot racing for example would have had essentially no military relevance - the Greeks never used them much, and certainly not after the archaic period.
The same could apply to foot races - they had one in full military kit, but also one in the nude, which obviously doesn't happen much on the battlefield.
All that to say, not all events were a direct reflection of military skill. The ancient Greeks appreciated and respected sporting achievements for their own sake.