Unlike most western migrants who wanted land, Mormons were mostly at it for religious freedom. Ever since they started growing in size in New York, they've had to move westwards in search of a place where they could practice their religious beliefs freely since they were prosecuted because of them very often. One such belief was polygamy in the society which was forbidden in the east coast. This is why they moved westwards and eventually ended up in the Utah area which is far away from New York.