Voters can take it into account. But you can’t elevate legal technicalities above democracy. People will not trust the people administering the election laws over the people they voted for.

It’s a “who watches the watchers” problem. Many countries have tried to impose the legal system on elections and it invariably results in destruction of trust in both elections and the justice system.

Your suggestion that voters can take information into account is precisely what is happening here:

Prior to the election, the information was illegally kept secret, so voters couldn't take it into account.

Now, in a new election, if this candidate stops illegally hiding the information, voters will be able to take the information into account.

Aside from that, there's the other matter that must be addressed, that of the criminal prosecution for lawbreaking.