One of the Big Theories for the premise of LOST was that the entire series was an elaborate mental dream, a collective dream or a computer simulation. It was not real. It was pure imagination.
Hurley was the perceived imagination engine. He was the one character that actually had vivid, structured and strong imaginary friends. One almost got him to jump off an island cliff, after telling him "none of this is real."
There were other clues that Hurley's mind was in control. The Others lab featured rooms that were based on psychological manipulation to mind control. The lab people were dressed and functioned like the doctors and nurses at his mental institution. Likewise, Hurley was able to move in and out of the institution like he owned the place.
Another strange thing was that Libby was in Hurley's same day rule at the mental hospital, but he did not recognize her when she showed up on the island. Hurley was friendly with everyone at the hospital; just like at the island everyone was his friend. The idea that Libby would fall in love with Hurley is something he could have longed for - - - recall, he lost the clerk young woman to his best friend.
The idea of the "collective coma" was a theory I stated when the series was still running along. It was basically that a series of coma patients were hooked together on a local area network to track brain wave activities. However, the coma patients minds are much more active than the patients outward appearance, so they have created their own virtual world (all of which predates our current AR and virtual reality headsets). Bits and pieces of the patients memories could have been used by Hurley and others to create the island world, the adventures and action which none of patients could fathom because of their medical conditions.
Locke's miracle recovery when he landed on the island is another example of "mind over matter" imagination. Locke believed he was an Australian outback hunter, but the wheelchair made that dream an impossible nightmare. He created his own path and adventure in the island world.
There is also a possibility that the main characters major accomplishments may have been embellished. Jack had a huge daddy complex. He suddenly became a miracle surgeon, to surpass his father's hospital status. But what if he was not an accomplished surgeon - - - but a mental patient who has hallucinations of his dead father. In order to patch things up, he dreams of a way to show his father that he was worthy of his praise.
It is the same motivational theme with his father's abandonment of him. It was something that stuck in Hurley's mind. He turned to eating to cope with the abandonment. It made him unattractive and unmotivated to succeed in life. He dreamed of being a rich and successful man. The only way that could have happened was the miracle win of the lottery - - - which in turn was his curse that he tried to runaway from.
Kate's own daddy issues made her runaway from reality. Her back story was one of manipulation and adventure but she never suffered any true consequences for her crimes. The unbelievably wrong trial was clearly the outcome of a delusional criminal.
All the bits and pieces of the LOST tangential story lines can be easily merged into one big mental simulation of events. An adventure for those who cannot adventure. Those people who wasted their lives without accomplishment, true friends or a path to enlightenment. Yes, LOST had its sci-fi fantasy elements but those can also be created in the imagination of one or more main characters.