Since you asked I will share some wild speculation, but to be clear I don't know how Apple's fraud prevention works.

Gift cards are the currency of modern confidence scams. Accounts that redeem a lot of high value gift cards are suspect for that reason alone. Buttfield-Addison makes it sound like this is common practice for him, so his account may have been on a shitlist already.

Apple may be so sensitive they'd close a suspect account after one failed redemption. It's also possible that card was first redeemed by an account that was closed soon after for fraud, and Buttfield-Addison's subsequent attempt linked his already-suspect account to the fraudulent one resulting in automated actioning.

Again, this is pure speculation, and is not meant to justify Apple's actions.

But it seems like it should be clear that the account that failed to redeem the card is, if anything, the victim. No?

I could see doing a lot of card redemptions as a flag, but then I think the next step is "what are they spending the credits on?" I could see a scam where you launder cash by turning it into cards, and then buying shitty and expensive apps. Thus paying apple 30% to clean money for you.