Legends are told by unreliable oral sources. making them twisted, meaning that this is not the story matoran is told but it is what (if this is made canon) is what happned.
The truth behind the legends. This is the kind of knowledge the common matoran would not know.
TLDR:
Creation of the Elemental gods is explained: To unite the matoran in tribes and structure them along with controlling nature.
The ruins all across the island is remains of ancient civilisations from the time when Ekimu (and in a way Makuta) was guiding the Matoran.
Explains what happened to Ekimu: got Jumped by Karzanhi
Explains why the toa suddenly have all powerful tools.: Ekimus relics that were scattered across the island.
Explains why Voriki and the mask of time is not used earlier: it was locked in some Ethenal realm of which Karzahni resides. Along with Woriki and the Big K himself. Also why The 7th tribe never had another toa as the Toas power was locked away inside Woriki while she was in stasis with the Big K.
And here we go:
Long ago,
Ekimu created the Island of Artakha.
Chaos reign, The unresting sea, the relentless storms, earthquakes, avalanches, devastating winters. and volcano eruption.
Makuta restore order and creates the entities, (they would become known as the Elemental gods)they would control the island.
The water is calmed, the fire subsides, the earth rests. the sky clears.
Ekimu then creates Rahi to inhabit this. Yet find them lacking and creates the matoran.
Giving them concessions, unordered and unguided they roam the island without purpose. Once again Makuta binds them to the elemental gods and begins to order them. Guiding them. Knowing that leaving them alone would they surely make more trouble. they assist in keeping the island in check.
Makuta orders Ekimu to take responsibility for his creations before more is made, else he will destroy all he has made. He binds the Matoran though masks but Ekimu but allows the Matorans to infuse some of them with great power. Makuta is currently unaware of this.
Great empire rises. The temples in the Tiko forest, the Great empire of stone, and the mangain and Ihu kingdoms form.
Then the 7th tribe appeared. Beliving Ekimu broke his promise and have created more matoran, Makuta stays true to is word and descends down manifesting as a monster that would destroy the entire island.
Ekimu knows that it is not what happned but in fact is other brother but cannot get to tell Makuta before being confronted by Karzahnii.
Ekimu battle the 3rd brother:i but is defeated.
Ekimu reliquary is however lost across the island along with the mask of time.
The first Toa is created and is guided to the relics of Ekimu and use these to fight Makuta. Now connected to the matorans the elemental gods acts in self defence and defeats makuta with the first toa.
Locking him away in an undisclosed location using the mask of time…
The 7th tribe is exiled into the storm north from the island.
Karzahni is then confronted by the Toa of the 7th tribe.
Voriki battles the weakened Karzahni.
Using the mask of time Karzahni is locked away. Along with voriki.
Aeons pass as the matoran rebuild, but unguided they fall to internal conflict and skirmishes that keep them from rising to their true potential
Several toas rise and fall. in that time.
It has been 100.000s years since the Great cataclysm. (Makuta decented onto the island to sink it back into the sea)
The mask of time finally shatters weakening the bond on Voriki and Karzahni that Allows Karzahni to transmit out his scheme to release himself. The fragments falls to the island below.
The Rakshi is guided by makutas word, now suddenly recive greater guidance as his prision is weakend too and is told to find and use the mask yet they prove insufficient to Release him. The Toa is raised and finds the mask and unfreeze the island along with Makuta. Karzanhi does guide the Toa as he it is only fitting that those that imprisioned him should relase him.
Karzahni prison is weakened to the point where Voriki can escape and returns to the island trying to warn them finds a civil war. As his prison breaks more and more, the Toa tries to use the mask of time to unfreeze more of the temporal issues.
Voriki confronts them (year ??) and warns them but eventually it is too late and Karzanhi breaks loose.
Thanks for reading.