All these gurus have an immensely large number of devotees who treat them as supreme beings or as the messengers of God. Scroll down to have a look.
From time immemorial, a vast majority of humans have been in need of guidance. Now, guidance did not come from some alien source but from a few humans who attained mastery over belief, thought and themselves. Since the spirit formed the core of their beliefs, they came to be known as spiritualists.