Do you think that Hillary tried to bait Trump into releasing his tax returns by suggesting that he is not as wealthy as he claims? No, she wasn’t really trying to bait him; she is already certain that he won’t release them. She was simply capitalizing on that certainty because, at least on that issue, she has him strategically check-mated.
How so? Trump believes as Nelson Rockefeller did--that the secret to success is to own nothing, but control everything. The result is that even if you find yourself on the losing end of a catastrophic lawsuit, because you own nothing, you have nothing that anyone can take from you. Moreover, if you are the beneficiary of a discretionary trust, though you own none of the trust property or income, you may nonetheless control and benefit from it all.
So, if Hillary now knows that Trump has so arranged his asset holdings, then she can be reasonably certain that the value of his personally owned assets are not as impressive as everyone is led to believe. Moreover, she can be reasonably certain that he does not want to reveal this fact to the public because it would only confuse them and foster allegations that he is a con.
How is this checkmate? Well, fact is, Hillary is right about Trump's exaggerated claims of personally-owned wealth. If he chooses to reveal that, she wins because she outed him. If he chooses to continue hiding the truth, she wins because he's perceived as suspect and non-transparent.