The argument that carried it
The appeal court accepted that the verdict did not answer a number of the defence's central points and did not explain why what was in substance a civil dispute had been classified as fraud. That is the recurring shape of an Article 159 case: the criminal charge and the civil claim describe the same events, and the only thing separating them is a finding about what the accused intended at the moment of the transaction.
Why a verdict that does not answer the defence is vulnerable
Article 307 of the Criminal Procedure Code requires the court to set out the reasons why it accepted some evidence and rejected other evidence. A verdict that recites the prosecution case and disposes of the defence in a sentence has not complied. Article 389.16 makes that a ground for quashing — and it is a ground about the adequacy of the reasoning, which is why it works even where the underlying facts are contested.
What remittal means here
The case returns to the first-instance court to be heard again before a different judge, with the appeal court's findings on the record. It is not an acquittal. It is a second hearing conducted in the knowledge of why the first one failed.