If the statements to either the bank or the tax authorities are false, that's a problem.
False statements are the base of a bank fraud case but you need more.
Is it possible to prove intent to defraud without a smoking gun? Sure, and I've convicted defendants (including wealthy real estate magnates) of fraud without them. But it's hard.
Usually corporations have accountants and lawyers who make that hard.
There is also an open New York Attorney General investigation into the Trump Organization, and we don't know its scope.
They are troubling and merit investigation, but significantly more is needed. /end