Greetings Student of the Arcane,
The expedient answer to your query is that magic and its unrestrained use, particularly in the crafting of conflict, leads to tremendous collateral devastation. Consider the chaos of hundreds of Mages hurling spells across the landscape with little regard for the lands they scorched and the peoples they obliterated. Change was inevitable. While the rulers of Westlock brokered the peace and the ensuing Mage War Accords, they did not do so alone.
Perhaps more history can be discussed later.
- Thessial, Faculty of the Arcanum