Is it political? Is delayed prosecution for financial fraud unethical?

Twenty plus years ago when I worked as an accountant for contractors documenting various types of financial fraud committed by the Trump organization for civil cases, the decision to not charge him criminally clearly was political. Civil courts in hundreds of cases found evidence of fraud, yet criminal charges were never filed. Politicians in New York and New Jersey, for their own reasons above my level of understanding, decided to not have their attorneys prosecute the criminal. No reasonable person can doubt that this failure of government was politically driven. We can conclude that any less powerful swindler committing the same crimes would have faced prosecution. I hold these state governments as primarily responsible for the cascade of international crimes that unfolded since that might have been avoided by normal timely prosecution.

Now, all these years later, with massive evidence of the same types of financial fraud compiled by multiple prosecutors and, in at least one case, is now in the hands of a grand jury. It appears that Trump will finally be charged and prosecuted for financial fraud.

Yesterday Trump put out a memo saying that any prosecution for any crime he may have committed in the past is political. He blames our society and the political climate. He does not take personal responsibility. Is he right? Is it right that we ignored his financial crimes for so many years and now choose to prosecute him? If the prosecution is politically driven, does that make it wrong? Or is a crime always a crime, no matter who commits it and who prosecutes it?

This is a question, I conclude, that is beyond my understanding of law, politics and legal ethics.