Donald Trump has decided that there will be no further criminal investigations of Hillary Clinton and the Clinton Foundation. Now he is showing some good sense. Some thousands of years ago the Romans pioneered the concept of being magnanimous. Instead of humiliating a defeated foe and "rubbing their face in he mud," the Romans would treat them decently and even help them to get back on their feet.
A criminal trial of the Clintons would attract the full attention of the country and the world. Such a trial would last for months. It would cost a lot of money and tie up many people. These resources could be better used to solve the huge problems that this country has.
In all fairness, a good team of lawyers could carefully go through Hillary's things and find some technical violations of the law. Of course that same team of lawyers could go through any of our things and find something technically wrong.