With the money the guy made, he will buy another PS5 and scam someone else. Eventually, he will have made enough money to buy two PS5. And scam two people. And then, three etc...
Having a PS5 does not make the Series S less interesting. The console has all the emulators you seem to have enjoyed, they are not going anywhere. You don't have to sell whatever thing you are not using for a couple weeks or a month you know. I have a Wii U at home that is precisely my emulation machine, I am not using it all the time, but I am happy to have it when I feel like playing some GC or Mega-CD or whatever.
Console has a ton of BC games that you will never get on PS5. As well as the Xbox exclusives, of course. And if you are interested in something in GamePass, at any moment you can take a month of subscription and try it. And I don't think that Series S is the one taking the most room in your house.
"Scam" implies the purchaser has been mislead or deceived in some way, let's not be dramatic in the usage of words here. Anyone buying a ps5 at scalpers prices haven't been scammed if they went into the deal knowing the price beforehand.
As for the op, I'd question how important these retro games are, if not (considering he hasn't touched the xss since the ps5 purchase the retro may not be too important?) then I'd sell it.