His ignorance doesn’t matter. If he signed off that there were controls, and that is true, then he is not liable.
Now look at what actually happened. This woman Edith O’Brien did transfer customer funds. Alarms went off in the control systems within hours, indicating a problem. So it seems like they did have effective SOX accounting controls.
What he is accused of, however, is ‘failure to supervise’. That is extraordinarily vague, and very possibly unconstitutionally vague. He told everyone to follow proper accounting policies, but there is always a chance someone won’t. If the system sets off an alarm, it is his responsibility to look at the problem, which he apparently did.