No it won’t backfire. He’ll act like a martyr no matter what happens or doesn’t happen.
The only difference is whether he’s held accountable for his crimes and pretends to be a martyr or not held accountable and still pretends to be a martyr.
As for the cult believing him, same deal. Following the leader blindly is what cults do.
True, I imagine he’d find something else to complain about. Although I also think that he had quietly slipped away (and not horde secret documents), people won’t feel so compelled about prosecuting him.