SPOILER ALERT!!!!
They did not all die when the plane crashed. Everything that happened, happened. The "flash sideways" is a sort of limbo that they go to when they die. Christian Shepard explained it: Not everybody gets there at the same time, but we all die. Jack died next to Vincent in the bamboo after he saved the Island. Hurley and Ben and Desmond are all left on the Island, and Sawyer, Miles, Lapidus, Richard, Claire, and Kate all leave on the plane. They all live after the show ends, but eventually they all find each other in the church when they die and move on together to the afterlife.
No, the whole show wasn't a dream. No they weren't all dead in the beginning. No, the Island wasn't really hell.
They did not all die when the plane crashed. Everything that happened, happened. The "flash sideways" is a sort of limbo that they go to when they die. Christian Shepard explained it: Not everybody gets there at the same time, but we all die. Jack died next to Vincent in the bamboo after he saved the Island. Hurley and Ben and Desmond are all left on the Island, and Sawyer, Miles, Lapidus, Richard, Claire, and Kate all leave on the plane. They all live after the show ends, but eventually they all find each other in the church when they die and move on together to the afterlife.
No, the whole show wasn't a dream. No they weren't all dead in the beginning. No, the Island wasn't really hell.