Trump defrauded NY state government, NY state voters, auditors, and any counterparties, like banks, who would make financial decisions based upon those documents.
Trump's instinct use all cash was correct.
If you want something to stay a secret, don't leave a paper trail of fraudulent financial documentation provided to auditors, tax officials, and financial counterparties.
If the Trump Org was domiciled in Florida in 2015/2016/2017, this may not have been an issue.