Its not so much smaaaart as, in this case, simple tax law. Trump owns a lot of real estate and business. Losses, in some cases, can be applied to taxes current and future. In Trump's case, his major tax deductions stem from Atlantic City losses in the early 90's and the real estate melt down about 10 years ago. The latter affected millions, myself included.
Taxes and deductions just describe money spent, but in different ways. With a tax, money is given to the government. With a deduction, money is given to a local business for supplies, or a charity, retirement accounts, financial investments, loan interest, capital investment. The same amount of money is spent (a deduction counts equal $ towards tax).
Some might say, but Trump, or anyone in same situation, lost money, why does that count towards a tax? Well, what was money spent on? Rent, paychecks, insurance, supplies, marketing, etc. Basically, the economy (all of us) receive 100% of those funds (losses). Whereas, when giving $10 to government, we dont see $10 in benefits.
Which should we prefer? Spending money on each other, or give it to the government?