Intent is one of the hardest things to prove in court. trump gave the DOJ a gift on a silver platter when he admitted it was his "intent" to hold back the documents. That is a game changed. The DOJ gave trump over a year of asking and prodding and he refused to give the documents up. Then he lied to his lawyer about giving them back and moved the boxes around in an effort to conceal them.
If trump gets away with these crimes, every person in prison for mishandling classified documents needs to be set free.