So they are just in connections with the hackers and they are in charge of making the money clean and not traceable, right?
Yes, most likely this is the case here, we are not sure how they know the hackers, maybe the hackers contacted them or what. But it's clear that the DOJ has trace the trail of the stolen Bitfinex hacked and identify it to Ilya Lichtenstein and Heather Morgan.
And based on the images and their lifestyles, they are living big and obviously you have to question where all the wealth is coming.
Old police work I think. When there is a big heist and someone suddenly living a high life, arise suspicions. People around them sure wonder where they get thier money and if they think like they can buy just about anything and brags about it on social media being a croc on wall street, it's odd. Normally they are sheep and wolves.

The DOJ didn't mention how they are connected to the hackers so this is still a classified doc? The term "Alleged" still makes them not guilty yet.