bitkoyn becomes too popular and too risky for criminals, so they switch to more hidden cryptothermia. Bitcoin is only one of the currencies, and if bitkoyn does not exist, there will still be people laundering money. People will always find a way to launder money. although I do not think it's very easy to launder money with bitcoins, This is because bitkoyn is a decentralized currency that does not belong to banks or financial institutions.