Possibly he has been selling fake goods and eBay caught up with him. Not everyone is happy with counterfeits.
Or he may have contravened any number of other rules and standards we sellers have to obey.
Or he may have forgotten to update the expiry date on the credit card he uses to pay his eBay fees. They get really upset about that.
Or he may have decided to stop selling on eBay. He could be On Vacation. Or he may have just quit.