To fool you in this case is the obvious answer, right?
I'm sorry for you when you in good service for this customer, thief, sent the money back as you trusted they were sending back the machine they falsely claimed was not to their liking. Thus breaking the social contract of online selling and buying IMHO.
I'd say with much experience of online selling and buying you do develop a nose for when something is off. Unfortunately, when you try to alert eBay to troublesome listings that give out such beacon signals, their proclaimed "AI" personell makes a decision nothing is wrong. Clearly because it's either stupid, evilly programmed or both. It's also close to impossible to find the correct category for fraud listings. That's intentional.
To me this means that eBay, out of some obscure reason, willingly partakes in fraud.