The Mueller Report will provide background, and may well provide proof to either pursue charges or "close the books" on them, but it is not the end of the story.
If he is guilty, he needs to be brought to justice. If he is innocent, he needs to have his name cleared. Either way, as an American, I have the right to know.
When the Founding Fathers created the Emoluments Clause, it was because of the simple understanding that even percieved personal gain from legislation harms both the Office and the Country.