THE LILLY THEORY

Another fan based theory was allegedly attributed to a cast member. It basically states that the series is all about the characters, and their collective fate to meet and interact on the island.

Fan Theory: All the survivors were fated, as John Locke has said, to be on the flight, and to end up on the island. In other words, the island chose them.

The pre-island connections between castaways keep adding up as the seasons went by and the flashbacks were interconnected at times. Incidents like Claire’s psychic convincing her to take the fatal flight (and playing a part in Eko getting on), Hurley making the flight despite all odds, Jack talking his way (or, his dad's body's way) on board and Sawyer getting deported lend a lot of credence. Every character we see seems to have had a reason for being on that flight of all flights.
Fans also use the following quote as evidence of this theory:  "Lost is a very big metaphor for every single character's mental state of being, psychological, and emotional state of being and we're on this island to be mentally, psychologically, and emotionally found. We were all chosen specifically because we will facilitate that for one another," said Evangeline Lilly.

Even though the producers  said early in the series that there’s a rational, scientific explanation for everything that’s happened on the show, that statement created skepticism with each passing season as the faith and mysticism have been become major themes.

In the post-ending conversations, the producers did say that the show was "character driven" and that the focus was truly on the characters. They also indicated that the final season was to raise the big questions about life, its meaning and people in one's life, but leaving those answers to the viewers to decide.

Since there was no rational, scientific explanation for the sideways universe or the parallel lives of the characters themselves, if LOST was merely a disjointed "character study" many people would find that a poor bait and switch.

There is no problem to have the story "hook" that a diverse group of characters were somehow "fated" to come together to do something important.

Fate is the development of events beyond a person's control, regarded as determined by a supernatural power. It is the course of someone's life, or the outcome of a particular situation for someone or something, seen as beyond their control. At times, individuals come to the conclusion that the outcome of a situation was "destined to happen,"  turn out, or act in a particular way.

In Greek & Roman Mythology, it is  the three goddesses who preside over the birth and life of humans. Each person's destiny was thought of as a thread spun, measured, and cut by the three Fates, Clotho, Lachesis, and Atropos.

"A fate worse than death" is a very old saying which foretells that something unpleasant will happen to someone. Perhaps, the characters being sent to the island was a fate worse than death, because they could not die until they redeemed their past - - - something that was holding them back. The fate theory is a subset of the theories that believe that characters were "tested" by supernatural beings. The reason for the tests is unclear, and the reward apparently was the ability to "move on" in the after life.