It's going through Ukraine.
Manafort seems to have been getting large fees to act as a conduit for dirty money from Russia through Ukraine into European Banks (Deutsche Bank) whence it came to the US.
Manafort is shocked, shocked, that his clients were money laundering. He, of course, knew nothing about it.
Sounds like Trump's luxury apartment sales were the far end of that process. He, too, will be shocked that all of that Russian money was illegitimate.
At least, that's where this looks like it is headed. Trump was willing to be the American front man for Russian money laundering. He's terrified of being exposed for his criminal behaviour.
There doesn't even need to be collusion for him to be a target for extortion.
This is my theory of what Mueller is up to.
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