Most people are terribly insecure and subconsciously doubt their place in family and society. When someone stands up in public and speaks with conviction it is immensely persuasive. Mix that with religion and you will also attract people looking for their place in humanity. The JW, Mormon, Xian stories provide a narrative that at once excuses weaknesses , provides a heroic path to redemption (do x, stay the course, get to the magic kingdom for the reward) and gives each person a vital role to play upon which everything hangs. This whole structure requires a figurehead, someone to lead and give authority. The more inaccessible the authority the better and so god becomes a sock puppet for an earthly leadership that assumes proxy authority. The desire for leadership and direction in life is a very powerful mental force that appeals most to those who do not have much power over their life ( uneducated, poor , ill and emotionally exhausted.)
Cold Steel how do you feel about being led by a prophet who is mentally incapable?
Mormonism has suffered this a couple of times ( and is currently experiencing a leader experiencing severe mental degradation.)