>>95890228
They didn't. It was Old Ones.
>
Under the Old Ones' influence, the world was irrevocably changed. The planet was moved closer to the sun, its orbit altered and its axis shifted to make the climate warmer and more habitable. Plants and life forms of infinite variety were introduced. The single mega-continent was split apart under the Old Ones' will, and the shifting plates came to rest in a manner more compliant with their design.
Lizardmen 6th edition, page 4.
>The Old Ones looked upon the world and saw its unique, boundless potential. They decreed that this world would have a central place in their unknowable plans. But, before those plans could be set into motion, they determined to alter the orbit and so warm the atmosphere. In time, the ice sheets retreated, verdant forests soon spreading to cover the newly revealed land.
>The next stage of the Old Ones' plan was the realignment of the tectonic plates. From the single mega-continent revealed by the retreat of the ice sheets, the Old Ones set into motion a plan that would see the formation of entirely new lands and seas, making the world conform to an established pattern compatible with their ends. This realignment would take many millennia, none other than the Old Ones knowing its final form or purpose.
Lizardmen 7th edition, page 6.