This is the problem for any international businessman going into politics: You got money from foreigners, and then you spent your money on your campaign. It doesn't matter how you laundered it, in between those events. The fungibility of money says you got illegal campaign contributions, unless you suffered a Chapter 7 bankruptcy and went completely broke between the two events.
Or maybe if you were very careful not to spend a single penny of your own funds on your campaign, including loans, people's time, appearances that have value, etc. You would essentially have to do absolutely nothing for the campaign!
This is another reason politicians use blind trusts. But they need to set them up before spending anything on their campaign. It is too late for Trump. He's already guilty, many times over.