IME it's because leaders are often someone we pin many of our hopes and fears on so that we don't have to pin them on ourselves and we rationalize not assigning the responsibility to ourselves by giving the leader supernatural abilities.

Unscrupulous leaders are a bit of ponzi focused on bringing in new followers who haven't lived to see them underdeliver and the beliefs of the new followers can help sustain the belief of old followers. Scrupulous, long lived leaders afaict are much more rare and are usually supernatural in ability, effort, and luck.