From this traumatic event, there are several theories that have been proposed about the show.
First, and most profound and hard to believe, is that Hurley was actually the person who died in the porch collapse. The entire show is Hurley's soul in denial - - - running away from the tragic event that ended his life. We know that Hurley was introverted but with a vivid pop culture, comic book imagination. It is possible he created his own virtual limbo to avoid acknowledging his own demise.
Or, more likely, Hurley survived the porch collapse, but caused the death of another person. We are never told the name of the victim, but there are two intriguing possibilities. One, is Hurley's imaginary friend, Dave. Dave appears to be Hurley's best friend. It appears they have known each other for a long time, since childhood. Dave is more outgoing and adventurous, so it is possible that it was Dave who pushed Hurley to go with him to the party. Or, two, the person that died in the porch collapse was Libby. Now, we saw Libby briefly in the day room at the mental institution, so Hurley should have recognized her when they met on the island (but he did not). That was always a strange situation. Hurley, being the most normal and comfortable in the facility, would have known everyone in the day room. Perhaps, that Libby was a ghost from Hurley's past there to subconsciously haunt him or save him, as Libby did on the island when Dave tried to get Hurley to jump off a cliff to "wake up" from his dream.
Yes, it has been theorized that LOST was all an elaborate dream inside Hurley's head . . . a creation of his subsequent mental illness, or as a result of his injuries from the fall such as being in a coma.
There is one key plot element in Hurley's story, and that is coming to terms with this incident. The only closure gets to this life event is finding peace and happiness with Libby in the after life (sideways world). So if one works back from that moment of resolution, we can track back how Hurley viewed himself. In the sideways world, he was a confident millionaire lottery winner who still had a void in his life, no soul mate. Tracking further back to the island world, he was an insecure millionaire lottery winner who believes he was cursed and never could be loved. Tracking further back to pre-flight 815, Hurley was an insecure loner with few friends and no real future in a career or in love. His best friend stole the girl he had a crush on. And if we roll back a little further, we have the story of Hurley and the porch collapse which traumatized him so much he had to be institutionalized in order to get treatment. It is at that place, Hurley learns of the numbers . . . which he uses to win the lottery in a miracle change-of-life fairy tale. But was that even real? Would his guilt cause all the curses after his good fortune (like his grandparent dying, the meteor hitting Mr. Cluck's, etc.). It could be that Hurley's deep neurosis kept turning his fantasy dreams into nightmares, culminating in the Flight 815 story.
It makes some sense that in order for Hurley to heal himself from the guilt of the porch collapse, he had to make it up to the one person he hurt most, that being Libby, the person killed in the accident. The means of accomplishing this resolution would be that Hurley's soul would have to search the underworld to find her, then make a connection - - - a strong bond - - - to find her again as her soul passed through the various levels of the underworld (as represented in the Egyptian rituals incorporated into the LOST sets). It was only after Hurley realized that death does not end life, but there is a rebirth with the ones you have lost, is when his fairy tale dream came to a conclusion in the after life church.
The Hurley dream theories are some of the most viable "unified" story structure theories in the LOST fan universe.
