Planar realignment

Before the Cataclysm, the elemental planes were undifferentiated other than into the core four--Earth, Air, Fire, and Water. Their admixtures existed, but were still firmly part of their parent planes.

At the Cataclysm, when the Left Eye of Qa'desh was ordered to destroy itself, it sucked in a large fraction of the ambient anima in the eastern hemisphere, and then backfired. It fed that anima, now tainted by strong abyssal influence due to the presence of the Nameless, back into the channels leading to the elemental planes. This abrupt backflow broke the careful meshing of the planes, and things started falling apart. The destruction reverberated through the Mortal plane, causing widespread devastation and natural disasters, including volcanic eruptions, earthquakes, subsidence and upwellings of land, gigantic storms, tsunamis, etc.

To prevent the utter destruction of the universe, the Great Mechanism reversed the normal flow of anima to the gods, absorbing most of them and completely depowering the remainder. It used those reserves to break the elemental planes into smaller chunks. Setting these chunks, the current planes, against each other provided some measure of stability. However, any spell that interacted with the elemental or astral planes was thus invalidated. Combined with the death of the gods and the drastic reduction in anima, magic in general ceased operation for nearly 50 years in Noefra and 10-30 years on the other continents.

Over the next 50 years, the Great Mechanism apotheosized new gods, and normalcy returned to the world.