explained

they were dead from the moment it crashed - the island never existed

walt was just hurt and unconscious and able to leave eventually

all eventually came together when they were ready to move on and accept death

ben wasnt ready and so didnt go into the church at the end. he was staying in limbo (purgatory ?)

the timelines were all different parallels as they could do anything in limbo

people died on the island when they were ready to move on


thank you