I don't know this to be true I guess it would take a lot of research to determine this one way or the other. I think some prophets may have been made up or even borrowed with ill intent to be used as controlling factors of the people.

I think in the eyes of a manipulator it would be easier to get people to follow someone else and control them through stories of a no longer existent or made up individual than to get them to follow you. In order to gain and maintain followers would subject self proclaimed prophets to an insane amount of scrutiny.

I think people who would manipulate others would take people who have stood as examples of unarguably good and then use them to influence to behaviors of others many years after such people existed and there was no longer a way to prove them fallible, much like the catholic church saints people and other religions choose prophets.

I think people who proclaims themselves prophets are either manipulators or crazy either way they are trying to manipulate others and have not thought the whole thing out. At the very least these manipulators have stubbed their own toe before they got going. Why put the spotlight on yourself when you can cast the light elsewhere where there will be less scrutiny at least then when you stumble it is easier to regain trust while claiming misinterpretation than it is to regain the trust of those who follow you and see you blunder.