That is probably the state violation, being pursued so that trump cannot pardon him as he can for federal crimes.
One just isn't the campaign manager in a foreign country (the ukraine, I believe) and not have a trailing Rolodex of contacts that certain other debtors to say, Russia, might have a very high interest in, and try to get access to.
Manafort also didn't disclose some connections on forms, which is enough to get him an indictment, too, that we know about. It will be interesting to see if trump was smart enough to shield himself from the hijinx. My guess is that he was not, there is smoke pouring out from his collusion orifice, but still no real smoking gun, or so it appears. It might take the 2018 election to get trump ejected.