[gumby]

Oedipus’s flaw was devinely inflicted (his curse/prophecy); attempts to thwart it (exposing him on the mountainside rather than, say, simply running him through with a sword at birth)* guaranteed it would result in the most terrible fashion.

The point was that Oedipus’ fate was sealed despite his “golden boy” greatness, not because of it.

* prophecy being prophecy, had he been killed at birth, that would have brought the kingdom to ruin: the gods’ will is stronger than that or any human.

[periphrasis]

Correct, in that as the play opens he has already unknowingly done the things that once revealed will destroy him, which were all the workings of the prophecy. However, in the action of the play itself, he still makes a fateful choice of his own to resolve the mystery of Laius’ murder to expiate the religious pollution causing the plague. A less conscientious king or a less able investigator would not experience the dreadful consequence of this choice: learning the truth. But precisely because Oedipus is conscientious and is intelligent, he uncovers the truth which utterly destroys him. It’s not merely that he was doomed before the play begins, but that he affirmatively makes a choice in keeping with his strength of character that reveals that doom.