Sorry, this is a classic Ponzi. I truly feel they would not have shut down if Bitcoin would not have crashed. Thei sustainable cash flow was from new buyers and the price of Bitcoin. There were no loans and no bot. Once the market crashed, their were no new investors and the cash flow was drying up. Once the owners had no liquid funds and had to delve into their profits, they exited. Pretty simple and pretty clear cut Ponzi. More people withdrawing and not enough investors