What I wonder about these schemes - why don't any of these "Money mules" just keep all of the money? If these guys had any enforcement capabilities in the US, they presumably wouldn't need money mules.
The mules are never in posession of "all of the money" - they handle a couple payments, after that they get the next ones. Sure, some of them might "keep" the money (they can't keep it, the victims have claim on that money and the mules aren't anonymous or protected) and not forward it, so the scammers need to recruit new mules.
The "money mules" may not realize that what they are doing is illegal. If they are people looking for part-time work and have already done weeks of menial tasks before being asked to transfer funds, they probably just think that it's part of their gig.