I smell inside job. The first person I would suspect is the victim.
Either he's in on it or he's just a moron that's trying to blame it on deepfake for his own fuck up. However, the bigger issue is why a company this size seem to lack any measures in place regarding large sum transactions. Don't you have to get multiple people to sign off on it?
If this was truly a deepfake scam (which I find hard to believe), the fact nobody noticed after a week shows there's no controls at the company.
But I agree with newty. It's suspicious. A finance guy being deepfaked by multiple people and at no time nobody cross communicated with anyone before the meeting seems fishy.