The way a Ponzi scheme works is that the person or group of people performing the scheme pays returns to its investors from new capital paid to the operators by the new investors, rather than profit from real sources. so you always have to have more new investors or it will fail, that is why they always find the conman when the stock market crashes. the new investors pay the ponzi and then the ponzi pays the old investors.
Bernie Madoff was able to keep his ponzi scheme going because he kept getting more clients/investors which helped him grow more and they didn't catch on because he was a very nice guy and everyone wouldn't suspect that from him.
A ponzi schemer is a person that is very sneaky, cunning and smart
Because no suspected him to do such thing, and because he was an adviser of the SEC.
i think he did it because he thought it would work and because he wanted more money and the more money he gets the more he wants.