Despite the role Jacob played in getting everyone on the island in Lost, he’s not actually to blame for what happened to Oceanic Flight 815. The plane crash, which took place in the pilot episode, is the incident that set the story in motion and brought all of season 1’s main cast to the island. Over the course of the series, multiple theories were offered in to explain what brought down the plane.
How everything was connected was finally explored in Lost’s last two seasons when it delved deeper into the two biggest players in the story, which were the Smoke Monster and Jacob, the island’s mysterious, so-called protector. Jack, Loke, Hurley, and the others eventually came to understand that Jacob was “the man behind the curtain” and the connecting tissue that brought them all together. He chose each of them as candidates to be his replacement and took steps to bring them to the island. While coming there may have been an accident of fate for several of the passengers, quite a few were there because that was what Jacob wanted.
There’s no denying that Jacob’s behind-the-scenes machinations are what drove the story, but that doesn’t mean he crashed Flight 815. Instead, this accident can be attributed to the actions of a different character – Henry Ian Cusick’s Desmond Hume. In a season 2 episode, Desmond came to believe that he brought down the plane when he failed to push the button in the Hatch. His theory was supported by the reveal that the one time that he didn’t push the button coincided with the timing of the crash. Since there were a lot of doubts at the time about whether or not the button actually needed to be pressed, it was unclear if Desmond was right, but later events indicated that he truly was responsible.
The explosion of electromagnetic energy that resulted from not pushing the button in the season 2 finale confirmed that the Hatch really was what the Dharma Initiative claimed it to be. This proves that Desmond’s claims in season 2 were accurate. He really did crash the plane, which underscores how instrumental the character really was to the show and its overarching story. Not only was the key to stopping the Smoke Monster in the Lost series finale, but he was also the person who made everything that happened to the main characters on the island possible.
As for where Jacob fits into all this, it seems that he took advantage of Desmond’s biggest mistake in Lost. Since Jacob possessed many powers as the island’s protector, it’s likely that one of them was the ability to see the future (at least to some extent). That explains how he brought everyone to the island. It appears that instead of crashing the plane himself, he used his knowledge of the accident to bring his chosen candidates to the island.