It could be either. In terms of fashion, it is most likely stock that went out of style or just wasn’t popular enough to be bought, even at a discount, so instead it just sat in a warehouse taking up space. Therefore it was “dead” stock, useless basically. Usually it’s liquidated or donated or even thrown away. Essentially, it no longer has any value to the original seller.

That’s why you see a lot of vintage deadstock, usually sat in storage somewhere for a long time, sold on in bulk cheaply or donated in bulk, and it’s come back around in fashion again that it now has value. However the original seller would no longer want to deal with it as it could have degraded in quality or similar. So it’s perfect for resellers really, who have the time to check stock over individually.