https://www.justice.gov/usao-sdny/pr/founders-samourai-wallet-cryptocurrency-mixing-service-plead-guilty says they plead guilty to "operating a money transmitting business that transmitted crime proceeds, washing more than $200 million in dirty money for criminals"

5 years is the maximum penalty for operating an unlicensed money transmitting business. They could have faced the same even if they did it on paper at that scale.