Crypto just enables these kinds of scams and makes them easier to operate. We have all seen the HYIPs offering very high interest, it's no different. It's also easier to get away with as it's psydo anonymous.
People still get caught though:
https://www.wired.com/2013/07/sec-says-man-named-the-pirate-was-running-bitcoin-ponzi-scheme/
Thanks for the explanation and the link - makes a lot of sense and is a good read.