Gavin stonewalled technical experts like myself that inquired about it after answering only a couple questions, so we can only figure out so much.

I think at the end of the day we should simply consider Gavin complicit in Wright's fraud. From that perspective there really isn't much to explain.  Sure, he was probably tricked at the time, but in the time since he's failed to withdraw his claims beyond saying that maybe he was tricked and it shouldn't matter.  His endorsement continues to be cited as a central factor in other people's belief.

I say 'probably tricked at the time'; because in spite of my low opinion of Gavin's character and capability I still have a hard time believing that he'd knowingly go along with such a transparent scam-- it just had too low a chance of achieving anything.  Wright apparently tried his con on other people unsuccessfully before Gavin.

Zectro posted a set of instructions for how to perform a fake signing that would have worked given what we (little) know about the irresponsible process Gavin used: https://twitter.com/Zectro1/status/1192576225413222405