It will be interesting to see where this actually goes. I do suspect that they brokered deals for funds rather than actually putting up theirs. Thus they could easily arrange money from less than wonderful sources and Trump would not need to know. It could even be CIA money. Private Russian sources tend to be pickier and more involved. They also do not take a joke well, and Trump would be unlikely to ever use their money any more than he would use Mafia or Drug money.
The German banks also have a serious reputation for real secrecy whose consequences go back to laws put on the books by Hitler. At least that is what i have been told and suspect it holds plenty of truth.
I think in the end this will be a nothing burger, but it is in furtherance of a program of harassment that will produce serious blow back at the polls...
Again almost by definition his specific type of business means dealing with multiple banks as a matter of course. And he was prepared to get tough with them as well because he could and often needed to. That did not stop access to money. Recall that he owns Trump Tower free and clear. He makes the banks work for him instead of the other way around.
Regulators are scrutinizing hundreds of millions in loans and a subpoena from Robert Mueller is expected.