There were never any actual classified documents on Hillary's server.
There were documents that carelessly still had classified paragraph markings on them, but those paragraphs were no longer classified. And there was enough information on the server to put together classified information. This certainly wasn't intentional on Clinton's part, but stupidly doing official business on an unclassified server was bound to get classified information on the server.
It wasn't enough to charge her with anything, but it did demonstrate incompetence. She was a hazard to national security.
Trump would, at best, be no better with doing official government business on an unclassified server. I would expect him to be far worse. I still wouldn't expect him to be indicted for it unless he was intentionally putting classified documents on the server.