A ponzi scheme works by having a person who gets an investment from a person and that person provides new customers to the schemer and so on.
Maydoff kept his scheme going on so long because his investors had trust in him so they never asked for their money back. His fake reports showed there was no illusion in front of these people to notice. He was safe and kept himself protected in every aspect. the only reason he got caught was the stock market crash that was unstoppable on his part.
to run a ponzi scheme the people who are giving you the money need to trust you completely so the person running it would need to be a confident person that is very trustworthy. to be successful you need to be able to blend in so no one will notice or become suspicious of you act.
The SEC didn't pay attention to the warnings about him because they thought he was one of them and would never do that. also since his books were so clean there was no clear evidence.
I believe Maydoff did this just because he could. All the people he took money from were just normal higher class people who could afford to lose the money so he figured he wouldn't hurt anyone that bad.