If T-rump's returns were released they'd likely show he has financial ties to Russia, either through loans (which no one else would give him) or through oil & gas deals (hence the explanation for appointing Tillerson as Sec'o'state.) Every other presidential candidate for the last 40 years has released their tax returns to show any conflict of interest. Trumpty Dumpty is going to take a big fall (hopefully a long one on a short rope) if we ever learn what he's been profiting from (and still is).