Maybe they already explain it somehow but I'm unable to figure out which timeline were suppose to be at.
There is 2 timelines,one where the the lostiest on the island the other where they never touch the island which related to the bomb incident.
Bomb exploded=plane crashed or the plane didn't crashed. No bomb exploded=plane crashed or the plane didn't crashed.
The 2 possible outcomes follows a flaw theory by Daniel. He stated whatever happen happens then in the end states he can change the future.So which one is correct.
-One could say the bomb created a new time line where there was no need for the hatch which results the the plane not crashing on the island.And the current lostiest are stuck in the incorrect timeline and need to somehow sync the conscious with the correct timeline.Which I suppose the reason why were are seeing the sideways flashbacks.
-However one could also say whatever happen,happen and the bomb seal up the mistake by the Dharma people to the point where the hatch was able to be created which results in the plane crashing.
At this point I'm more toward that whatever happens happens,where at the bomb exploded and worked in the result to create a hatch and the plane get hit later on. And thats why in the sideway flash back we see the island underwater cause the bomb wasn't used which results in the island slowly decaying to it eventually sinks However if thats the case whats the point of showing the sideways flash backs.if that timeline will never exist now.