I had the same question. If I had to guess, I’d say they buy bundles of games often, where the bundle includes a game they already have but 4 games they also want. The price is right and the condition is good so why not? If a cart ever fails you have a backup right there. If the value goes up (likely) you can sell one of the copies down the line.

Edit: nvm, op replied here

Question. Who owns these lemmy sites? I understand it’s decentralized. Can someone breakdown exactly what that means? Who, if anyone, owns these sites/servers, how it all works?