Trump took classified information during his time as president and failed to return them
When asked to return them he failed to comply until forced
When forced to comply, he still kept many documents the government knew were missing and lied to the government and his lawyers indicating that they were returned
Was caught on tape admitting that he knew they were classified and that it was wrong for him to have them
The first bullet point apparently happens often (Biden, Pence, Hillary have all done similarly in the past). Trump is singular in that he didn’t readily comply with the request for the return of documents and the consequent lies to the government (also illegal).
There’s a LegalEagle video which sums it up: Trump’s Bombshell Federal Document Indictment
Essentially,
The first bullet point apparently happens often (Biden, Pence, Hillary have all done similarly in the past). Trump is singular in that he didn’t readily comply with the request for the return of documents and the consequent lies to the government (also illegal).