Concealing information for the express purpose of changing the outcome of an election is a crime. It’s always the coverup that gets you. Ever notice how Trump was able to get away with constant crime all this time? It’s because it was blatant and done in front of everyone. Just like soliciting Russia to hack Hillary: if he’d done it in secret he’d have been charged, but he did it in front of the nation with cameras on which gave him plausible deniability that what was in his heart was a crime and not a little jokey-poo.
This time he tried to cover it up, creating a trail of paper and witness to prove that he knew what he was doing was illegal.