Just Saving the World, the Finale by Jhisc9999

There are many confusing aspects of the two timelines that I think I have a handle on, finally. First of all, I believe that whatever happened, happened – including the H-bomb/incident and the creation of the Alt timeline. The Alt timeline has been running parallel to the original timeline since 1977, but it’s start date was 1974, coinciding with the last time jump that brought the Losties there. So they accomplish their task and flash back to their correct time in the original timeline, not knowing that they have created a parallel timeline that is running 3 years behind their own.
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The Alt does not include any of the influences of the Losties. So why is it so different? How could the lack their presence there have made such a difference in everyone’s lives and resulted in the island underwater? I believe there are two explanations:

1. The timelines have been bleeding together for the Losties ever since the Alt was created, but only on a subconscious level. The Alt has the advantage of being three years delayed. So the Losties in the Alt have been influenced by “intuition” to make better decisions.
2. Faraday’s plan to neutralize the pocket of energy had a different effect that was only realized in the Alt timeline. The energy was moved to another location on earth. With the energy gone, Dharma gradually lost interest in the island. Ben and his father left. Dr. Chang left with his family. The island began to sink.

But I believe the Alt is destined to end when Desmond turns the failsafe key in the original timeline. I proposed in earlier parts of this theory that the hatch was saving the world, the Alt world, by preventing the universe from self correcting and destroying the Alt. I think the Alt Losties are going to “let go” when they all finally get back together and, with Eloise’s help, they will be able communicate and assist the original Losties. They need to convince them to help Desmond enter the light so that he can flash back to the moment before he turned the key. Whatever happened, happened does not apply to Desmond. He must not turn the key this time. This will save the Alt and destroy the original timeline.

But what about MIB, Jacob and the “light” in the Alt? MIB and Jacob were bound to the island and died with it in the 70’s. The light moved with the energy to another place on earth. Perhaps it will form another island. How are islands created? Volcano.