I disagree. The accused's computer was searched and nothing was found. A person owning the account from which the messages were sent is not enough evidence to send that person to jail, not in any sensible justice system. What even is the point of the search, if the outcome of the search does not matter? What difference would it have made if they had found evidence on that computer? This is not a rhetorical question.
Also, the accused shouldn't have to prove that he got hacked, especially not in the absence of any evidence on his computer. The burden of proof is on the accusation.
More generally, a judge needs to know that identity theft is a thing, because it is very much a thing. A judge who doesn't know that is incompetent. Incompetence is not a valid excuse for ruining someone's life. If your argument is that we should accept that judges are ignorant and tech-illiterate, and not expect that they fulfill their mission, then it is a bad argument. The judge decides which evidence is admissible, and bears the responsibility for that decision. I am not arguing that judges cannot make mistakes, they are humans and so they make mistakes all the time, it is inevitable. I am however arguing that this mistake is so gross, and with such consequences, that it warrants punishment.