Disclaimer: I don't own LOST, anybody who is affiliated with it, or the characters (although I wouldn't mind owning Sawyer and Mr. Eko).
Chapter 1: Time Travel is Such a Complicated Nuisance
"What are you waiting for, you son of a bitch!" The bleeding Juliet screamed as she hit the H-bomb repeatedly with the rock, with as much strength as she had left in her broken body. She wasn't going to die a horrible death for nothing. She wasn't going to give up happiness with James and sacrifice the chance to ever see Rachel again for nothing.
She wanted to end it all. The island. The goddamned island that had brought her every emotion a human can feel over six years... within three decades. Time travel is such a complicated nuisance. Daniel Faraday knew that… especially when his younger mother shot and killed him mistakenly thinking he was an enemy… and then gave birth to him a few months later. And after the woman he loved bled to death in his arms because human brains can't always handle jumps through time-space.
They were all coming to realize that. Every single person involved in the time travel.
And as Juliet finally succeeded in her final goal, a bright white light appeared and that was the last thing any of them remembered.
That bright white light in 1977 would become known as "The Incident". Out of all of them, Miles was right. They all looked down on him for being just some pot-headed medium who could talk to ghosts. And it turns out he was smarter than a theoretical physicist and a spinal surgeon. Kate had an idea as well that setting off an H-bomb was never a good thing. Of course, out of all of them, she was the least affected by the time travel. She was only an infant in 1977, and would have no connections with the island for 27 years, except for "Jacob's Touch".
Miles deducted that setting off the H-bomb wouldn't prevent The Incident from occurring. It WOULD BE The Incident! Had they really succeeded at preventing the crash of Oceanic Flight 815, they would have never crashed on the island to have gone back in time in the first place. He would have never been on the damned freighter. Faraday, it seems, was wrong about the Variables. Nevertheless, it was his destiny to be wrong about the Variables. It was his destiny to die at the hands of his own mother. She raised him up for that one purpose: to go back in time and be killed by her so that The Incident could occur.
Alternate timelines are nothing more than theories. And after The Incident, they were right back where they started – 2007. Only Juliet was dead. At the bottom of the shaft. Sawyer tried in vain to save her… almost like a madman. Kate helped him, despite never caring much for Juliet. She did care about Sawyer and didn't want to see him broken-hearted. By the time they finally got to her, it was too late. Juliet helped him to get over Kate's "death". Now that Juliet was dead and Kate was alive and well, the tables would be turned.
Out of everyone who had ever died on the island, Juliet was the bravest. How many people can say they died by setting off an H-bomb while lying right next to it?
Sayid was close to death as well, but there was still hope for him. He was a Candidate, after all.