a money laundering charge requires an illicit origin, which means it can only be a tacked on charge after charging or proving someone was involved in the illegal activity.
the government just doesn't know, they just find everything this couple did to be super suspicious. they clearly had control of an excessive amount of cryptocurrency that they were reintegrating into the economy. the government doesn't seem to know if they were actually involved in the heist, or how, or to what extent.
simply obfuscating money isn't illegal. obfuscating an illicit origin is. lets see if the government can get to the bottom of this "conspiracy to obfuscate money of an illicit origin".