Timeline of Events

The three Golden Goddesses, DinNayru, and Farore create Hyrule and the lifeforms that inhabit it.

Upon their departure, they leave behind the Triforce.

But whether intentional or not, a parallel world of Lorule was also created alongside Hyrule, along with its own version of the Triforce and inhabitants.  The two worlds are inseparable.

The Goddess Hylia appears in Hyrule, as well as Demise in Lorule.

The people of Lorule lust after the power of their Triforce.  We might infer that Demise was involved with this.  In any case, the leaders of Lorule decide to destroy their Triforce in order to prevent it from falling into the wrong hands.

Eventually, this causes Lorule to decay into a harsh world, possibly becoming what is known as the Dark World.

In Hyrule, on the other hand, the Triforce is entrusted with the Goddess Hylia.  At this time the Ancient Robots, Parella, Kikwi, Gorons, and Mogma live on the surface, as well as Humans.

Hylia's Chosen Hero also exists at this time.

The Demon King Demise finds a way to escape Lorule and enters Hyrule with an army of monsters, bent on obtaining that world's Triforce.

He forges a sword and infuses it with the power of a spirit, Ghirahim.  The design of the sword further suggests an origin in Lorule.

To be continued...