Excuse me, he took classified documents with him from secure areas to four different locations (that we know about) over several decades. A lot has been made about where Trump had documents at. Biden had boxes of classified documents in his garage.
There aren't exceptions made in the law. This is similar to Jim Comey saying he didn't believe it was Hillary Clinton's intent to break the law after it came out that rather than submit under subpoena all emails on an illegal server she deleted 33,000 and then destroyed all devices that would make it possible to retrieve those emails. This is the kind of justice that makes Republicans believe there's a double standard.