As a general rule, ignorance of the law is not a defense, especially when the law violation is something that the culprits should know. That doesn't stop the Trumps from trying by feigning ignorance and dismay.
Donald Trump Jr. was aghast, "they're going to charge a guy who's 75 years old on crimes of avoiding paying taxes on a fringe benefit"
"These are employment perks," Eric Trump told host Raymond Arroyo. "These are... a corporate car which everybody has, I guarantee you... there's people in this network that have corporate cars, there's people in every company in the country that have corporate vehicles. This is what they're going after. This isn't a criminal matter."
“They go after good, hard-working people for not paying taxes on a company car,” former president Donald Trump said at a rally in Sarasota, Fla. “You didn't pay tax on the car or a company apartment. You used an apartment because you need an apartment because you have to travel too far where your house is. You didn't pay tax. Or education for your grandchildren. I don't even know. Do you have to? Does anybody know the answer to that stuff?”
Yes, honest taxpayers know the answer. A car and lodging for personal use is considered income and subject to income tax. A CFO isn't like a traveling salesman in which driving a car or needing a place to sleep away from home are part of the job. Perks like the company paying for school tuition for kids or grandkids is considered income and subject to income tax. There is no magic age cutoff when in-kind income is not subject to income tax. Furthermore, not everybody has a corporate car, and those who do must declare its value for personal use.
Incidentally, in 2016 Donald Trump said, "I think nobody knows more about taxes than I do, maybe in the history of the world." Source That undercuts any attempts by Trump to plead ignorance.
I am going out on limb and suggest that the Trump Organization also benefitted financially and tax-wise from their tax scam.
In 1989, Trump took a dim view of tax cheats, in particular of Leona Helmsley who was then facing trial on charges of tax evasion and fraud for which she was later convicted and sentenced to jail time.
At the time, Howard Kurtz of the Washington Post wrote:
Donald J. Trump has shaken the onyx and marble foundations of the hotel world by calling his equally overpublicized rival, Leona Helmsley, a "disgrace to humanity." In a deliciously vitriolic letter to the self-proclaimed Queen of the Helmsley hotel empire, The Donald (as he is called by his relentlessly glamorous wife Ivana) displays a previously hidden capacity for venom by slicing The Leona into tiny little pieces.