If you are doing business with someone under criminal investigation you may well find yourself under scrutiny as well. If you are talking on the phone to someone who’s phone is bugged your conversations may well end up being recorded.
Neither of these indicate guilt on your part but they certainly give the investigating agency a reason to snoop and ask questions.
Manafort was used only as an excuse to listen to Trump.
A lesson to Americans. Never talk to foreigners. How can you be sure they don’t have any criminal ties? Some special prosecutor may come gunning for you (even if there is no law you have violated).