Having a mentor can only make the journey fast, but it is not every successful person that has a mentor. We said every successful person has a mentor. What about people like Isaac Newton who created Newton's law, James Prescott Joule who created Joule's laws, etc.
I believe what most successful people have are inspiration, staying hungry to make an impact, and dreaming big.
They probably also have mentors from their childhood or somehow they went through and had some conversation. But I agree to you that they have inspirations on how they have looked into the world and the wonders that it has got. Are they successful with that case? I guess they are and we can simply say if they've got parents, friends, teachers or whoever they got that inspiration might be a mentor in their own treatment and volition.