So somebody hacked my Ebay account. I buy lots of stuff on Ebay but haven’t sold anything for a long time. Yet the hackers used my account to try to sell things, mostly cell phones.
Why wouldn’t they just open their own account to do this?
Or were they somehow getting money for the phones and not shipping them and then I’d get blamed and be on the hook for refunds?
What’s the scam here?
BTW, Ebay security fixed everything and were quite good. 
It seems that this is a common scam. You were probably ‘spoofed’ rather than hacked and you may have unwittingly given the thieves your details by clicking on a spoof email.
When they use an account like this it seems that they persuade buyers to pay outside the eBay/Paypal system using an unsafe payment method like Western Union, which is just like sending cash. Of course, those buyers will never get the goods and when they complain to eBay, they will get nowhere.
Ebay rates the reliability of buyers and sellers. If you’re an established seller with a good rating, but haven’t sold anything in a while (and thus likely don’t carefully monitor your account), you’d be a prime target for this. The sellers are hijacking your favorable seller rating to convince potential buyers that they are a reliable seller.
They may or may not be actually selling anything. If they are selling over-priced goods, they can potentially keep the scam going for awhile, while your seller rating degrades. Or, as you suggest, they might have been “selling” nothing, as a short-term scam. Or, they might even be semi-legitimate but new sellers that just wanted your rating (although that last possibility isn’t too likely).
Or selling illicit goods via an account that tracks back to you. An aquaintance of mine got busted selling pot this way.
Customer Go to Amazon and order a certain overpriced used book, your stuff shows up a few days later.
They were looking to take advantage of your feedback rating. I almost always look at that number when deciding whether to buy something. If it’s over a hundred I’m fairly comfortable buying from them. Less than ten and I might be a little leery.
This in addition to the reasons listed previously.
As your account is old and the authority of your profile is very high. He is using your account to loot people.