You do not need to have a mentor before you can become successful in life. There are many successful people in life that does jot have a mentor.
Some people only like after a role model and they may want to be like such people and work towards it.
But know that success is not about having a mentor or looking after someone as a role model. It is about how smart you are in achieving successes. Opportunity and exposure are also very important.
You are absolutely right, having a mentor isn't a criteria for success, you can become very successful without having a role model or any one you look up to. Achieving success is all about dedication and consistency to you goals and ambitions. As a matter of fact having a mentor without having a drive or prospect would take you no where. Some people are of the opinion that having a mentor isn't necessary and believing in yourself and working hard is the only thing that matters, it's not entirely correct but it actually makes a lot of sense.
Most "mentors" that helped the successful people are just people with network. For example lets say I have no money and no product, just an idea, who would care about me? Millions of people around the world has that, and yet if we do not have help, we can't do anything about it. Let's assume that whatever nation you are in, president is your uncle, or grandfather, which would make you rich of course, but let's assume that you are still not, you would just go to any bank, say president is your uncle, get any loan you want, easy, they wouldn't dare to reject you, and even if one does, the other would accept it.
You want to make a product, go to any factory, ask for help, who would reject presidents nephew? Nobody, and like previously, if one does, the other won't. President is a big one, it could be just some industrialist, it could be someone totally unrelated to you, but if they are your mentor, they can make a phone call, and get you whatever you want in life to progress your situation.