I'm sure you all heard the theory that is pretty much fact. Danny brickwell caused the arrowverse to unfold. After shooting Malcolm merlyn's wife, Malcolm planned the undertaking and was the reason Oliver and Sara were on the boat. Oliver and Sara survived being shipwrecked on an island, and Oliver found a friend, later turned enemy known as Deathstroke. Oliver survived for 5 more years until he was rescued and came home. He became the vigilante known as the Arrow, and Sara was discovered to also be alive, and took the identity of the Canary. The Arrow inspired another man known as Barry Allen to become the hero known as the Flash, who inspired a man named Eobard Thawne. He went back in time to kill Barry's mother, creating the Flash by starting a particle accelorator that turned other indiviguals into metahumans. After the Flash and Arrow defeated an immortal madman named Vandal Savage, Malcolm restored him by unknown means, causing the formation of the legends of tomorrow.