The criminal buyers' plan is to buy bitcoin, maybe shuffle it around a bit to hide their tracks, and sell it as soon as they can. They don't want crypto, they want cash, and they need buyers to get that cash. That goes for everyone, in fact. The only way criminals are different is that they don't want higher prices, they want high volume, so they can sell it fast without losing too much.

A unit of cryptocurrency is a nothing. If you never sell it, it's useless and worthless. Everyone buying crypto is planning to sell all of it. They always need more and more buyers to keep driving the demand up, to in turn keep driving the price up. Eventually, there'll be a time when there are too many sellers and not enough buyers. Maybe a major recession hits and people decide it's a good time to cash out/bad time to make risky investments. Maybe regulation starts scaring people away. Maybe mainstream news coverage turns hostile. Regardless of which, people rush to sell, and as the buyers dry up, they start taking whatever price they can get. The price plummets. Sell orders accelerate. Line goes down. Pop. Then, stories of people losing everything circulate widely, cementing its reputation as worthless and scaring off any speculative buyers forever after. Just like Beanie Babies.

Just like Beanie Babies, there'll probably be some buyers and sellers forever. Just not at a high enough volume to make it worth a criminal's time.