Complex sentence: Some think that the large "Walser" migrations took place because of conflicts with the valley's feudal lords, while other theories say it was because of overpopulation and yet others that they were reinforced by the respective local authorities in order to settle previously unpopulated regions.
Split into simpler sentences: Some think that the large "Walser" migrations took place because of conflicts with the valley's feudal lords. Other theories contend it was because of overpopulation and yet others that they were reinforced by the respective local authorities in order to settle previously unpopulated regions.