There is really no way of knowing, I suppose. He was just searching for Navi, so perhaps he just wandered off into a forest to look for her. He stumbled into the forest with the skull kid and passage to Termina by chance, I suppose.
I'm not too familiar with Zelda Theory, since I typically avoid it to keep myself from having to learn all this stuff about timelines and everything else, but I do believe I can answer this.
This is how it goes:
Link is looking for Navi in the woods, when he encounters Skull Kid. We are all...