In 1959 the US department of defense artificially constructed the island to use as a laboratory for work in areas including eugenics and cryogenics.
It was eventually hoped to use nanotechnology to bring about world peace.
The plane crash was purely fate. The survivors of flight 815 are actually all dead and the "monster" in the jungle is actually an experimental new type of four dimensional hyperfluid.
The Others are loyal devotees of Alvar Hanso.
"The incident" mentioned in the orientation film refers to a situation where experimental nanotechnology accidentally escaped from Dharma's laboratory and if the button in the hatch is not pressed every 108 minutes it will trigger a nuclear war.
