I am currently writing a story that takes place after what we would call World War Three, in a post-war setting. In this setting, magic exists along with creatures created by radiation from WW3 and magic. Many kingdoms and settlements exist along the Post-War Earth.
In the story's history, four main time periods exist: the Early Period (pre-history period), the Exposition Period (we live in this period), the Pre-War Period and then the Post-War period. This question mainly focuses on the Early Period going into the Exposition Period. During the Early Period, magic existed on Earth and all forms of life could use magic in it's raw form. Humans were able to refine magic and use it to their advantage, creating towns, agriculture and etc. This use of magic swiftly lead to advancements in technology and the beginning of industrialization.
As humans began to use the valuable resources that Earth had to offer, magic slowly began to disappear. This lead to the eventual loss of magic and the memory of it.
Would it be plausible to say that the Earth absorbed the magic it held to keep itself alive and that's why it all disappeared? Would it be safe to say that magic that is held within objects like crystals or tomes would not be affected by the Earth?