In previous episodes Oceanic Airlines has been seen in flashbacks with the Others (the mobile in the nursery during Claires time in the medical hatch). But from the finale it seems that the crash was an accident caused by Desmond not pushing the button. Does this mean that the Others have no ralationship to Oceanic as previously thought and the mobile was just planted by the producers to start discussions amongst people? Also it seems a stretch that the plane crashed by accident since everyone on the island seems to be connected in one way or another (Locke's quote on a previous episode about crashing specifically on THIS ISLAND and Locke's legs and Rose's cancer being cured).
I don't think Locke's legs and Rose's cancer being cured point to anything other than the healing properties of the island. I don't think their ailments play a part in why they specifically survived the crash when others didn't.
I do think that Desmond not pushing the button caused the plane to crash, but I also think that the island itself "picked" who would live and who would not. How, and why, I don't know lol.