"The three tribes were different, and the fear of the other is strong. Faust sought to create unity between the three tribes with the Golden tree, but when that failed the divides between ponies grew wider than ever, leading to wars between ponies that you couldn't believe the destructive scale of. It wasn't until they realised that no one tribe could win that a truce was called, leading to the rather chilly situation that preceded the Exodus. Negative energy was rife, and threatened to push ponies over the edge into another war if not managed."