He was convicted of a state law. Not Federal.
To be convicted of violating the state law he also had to be guilty of some other law. Nobody knows what law that was, but both tax law and election laws mentioned as possibilities are federal laws.
In fact, to even be CHARGED with violating the state law he had to be guilty of intending to commit or conceal some other crime. Bragg should have had to claim the specific crime that allowed him to bring expired non-felonies as if they were felonies, to the grand jury and to Merchan who ran the grand jury. Did he? That should have been the first thing Merchan required.
Trump was guilty of nothing. The jury, prosecutors, and judge, however.... are a different story.