It all depends on how good the idea, and if that person has the incentive to put the work required to get it done. If someone creates an amazing app that a ton of people use, if they are able to sell it to a company for billions, then they're a self made billionaire.
It is possible to become a self made billionaire, but it would be very rare and difficult to achieve. Such a small portion of society becomes billionaires and much less self made. But the American dream has made the path possible and many people attempt it, if only a very small few make it.
Billionaires can become self-made, but they need loans, investments and lots of employees at their companies in order to make it happen. Someone, somewhere, has to be willing to spend money on what the billionaire is selling in order for that person to make money. There are billionaires who make money from seemingly little, but it takes a lot of consumers for that money to be made over several decades.
Yes, I believe that it is possible for people to become self made billionaires without help from anyone, because there are a lot of talented people that can make it on their own. There are people who have great ideas and who put those ideas to work. There are always others involved, but people can achieve anything on their own.
I do not believe it is possible to meet success without the help of anyone. People don't succeed all on their own, it always takes a partner or a group of people to help you. Therefore, I believe it is impossible for a person to make themselves a self-made billionaire just alone.