Given the numbers Donald Trump is working with, I can't see any reason to believe that a 900 million dollar loss in a single year proves that Donald Trump doesn't understand business. On the contrary, it may very well say the exact opposite. The tax law is a byzantine collection of carve outs and political give backs to every special interest over the last 75 years who managed to buy a congressman. Managing tax liability is a deeply strategic issue for a growing company, and 'write downs' in one year can reap considerably larger benefits in later years, if properly handled.
Had Trump filled out a short form it might be a different story, but that is clearly not the case. His taxes are a reflection of a snapshot in time of varied interests, and any businessman worth his salt can make a snapshot looked either good or bad given the complexity of our current tax rules. in fact, in most cases that's precisely what you want to do. You want to make things look as good as you can for the quarterly report, and as bad as you can for the IRS. And that process is performed 4 times a year by every public company in the country. Trump's interests are private so the rule set is even more easily manipulated, and the goal is very much the same.
As far as I can tell, the goal of team Clinton and the Times isn't to say that Donald Trump is stupid, or that he lied, cheated, or broke the law. The goal is to show him as having been 'unfair' by not paying more in taxes, even though the law said he didn't have to. They want to paint him as having 'denied the government its fair share of his earnings'. This strikes me as a very tough sell. There isn't a single working American who doesn't wince a little on tax day, and if Trump, as a private citizen, managed to use the rules to his advantage, I don't think it's going to annoy anyone but the Times and the rest of team Clinton. He didn't tie the girl to the tracks or drive the train toward her, he just bought a ticket on the train like everyone else. But they want us to believe he's a villain anyway, just because he sat in the first class car.
I think this says something very important about the state of modern liberalism. The whole enterprise has completely lost touch with reality. The reason they believe Donald Trump should be paying more in taxes is because they 'feel' he should. That's it. That's their only real complaint. No law broken, no rule violated, no unethical goal achieved. But they are still acting like he's done something wrong. That says an awful lot about their worldview.
In my mind, it means they are no longer capable of having a discussion about reality. Their perspective no longer intersects with it enough for them to recognize it when they see it. It isn't just racism and misogyny where they have abandoned reality, it's everywhere - every political discussion. They can no longer see the forest, or the trees. To them, it's all just so much unprocessed wood pulp that the people are being denied the use of because some rich guy refuses to come chop them down for them, or something like that.
Thankfully, they are making their views clear, and the people have begun ignoring them in droves, like they always deserved to be.