Yeah, like TS said, he touched it once in OoT, and it split. So he gathered it up. He killed Link and Zelda (and then his entire army, for good measure), and rejoined the three pieces to get his wish. And that's how LttP happened.
Good point! Plot hole is a poor choice of words. But I feel this slight sensation that the entire split Triforce thing was an interesting idea, and probably just a concept used to explain why Ganon had the Triforce of Power in Zelda 1 and the cartoon (yes, sorry for bringing up the cartoon. Lol).
Except that's not why it was split there. It was split in OoT, and Ganon regained it some time before LttP. But then Link defeated him, and obtained the entire Triforce. It was passed down in the royal family, until, at some point, they decided not to keep it all together in case somebody were to take advantage of it. So they hid the Triforce of Courage in the Great Palace, passing down only Power and Wisdom from one ruler to the next. Ganon tried to get the Triforce from Zelda once, but failed (according to the Zelda II backstory and Hyrule Historia). So he tried again, building an army and stealing the Triforce of Power from the royal family. He made a grab at the Triforce of Wisdom too, but Zelda split it into 8 shards, leading into Zelda 1. So Ganon having Power in the first game is actually unrelated to the split that occurred when he tried to take the Triforce in OoT.

