"The rest" is really what they're looking for. If he had $80 million in expenses paid to contractors, the identity of those contractors (from the copies of the 1099 or similar forms for them) would likely be of great interest to people.
You didn't address my other point: How did they know it was a real copy of the return, and not a fake?
Your supposition at first said nothing about a possible “fake” that I could see. You supposed they knew something additional about it, where it came from, legally even.....I just showed you the logic that both the reporter’s claims and your supposition they “knew” can’t both be true. It makes no difference about your additional supposition - it’s just meant to further muddy your original thought.