The SWIFT issue is a matter of public record. Sourcing about “why” it happened is speculation. It is yet further speculation to say Benedict resigned over it. It makes no sense that he would resign because of this. He wouldn’t capitulate, to surrender the Church for a money issue. Even as a theory it doesn’t make any good sense.
As I noted. He had decided in the summer 0f 2012 to resign. He told Ganswein in September. SWIFT had nothing to do with it.