Ehh they are buying from one person and selling to another so they absolutely sell shoes.
The Terms and Conditions make it clear that is not the case. They are the intermediary, matching a buyer with a seller and taking a cut for the service. No different to eBay over the years in that respect.
What was revolutionary about StockX was that they did Authenticity Verification at the same time. Those of us who were buying and selling back in the early 00s know, it used to be the wild west out there... StockX made distance selling less of a headache.
The entire case is built upon them taking this cut on reselling and making money on incorrect authentication.
Now, you might wonder why Nike cares?
Some of their kicks probably get misrepresented all across the globe every day, in-person. Are they wanting to do the authentication themselves? Cos they don't offer it right now...
If its because they don't like someone else making a cut on their shoes selling above resale... well, make more! Or provide your own marketplace.
Rolex have done this. They tried hard to stop people buying a Rolex at 9k and turning round and selling it for 15k the next week, but ultimately there's no definitive way to stop it. So now they've set up their own resell and verification service. Through their authorised dealers only, you buy a 2nd hand Rolex and they've both legit-checked it AND serviced it, so they're trying to get in on the resale market by winning people's custom.
But unless Nike does the same and provides a resale and/or authentication service, I really don't see what their end game is.
If StockX goes under... well first of all there is still GOAT, and I'd say that's bad for everyone because then there is no competition in the market. But if both went, if Nike kills the resell market.... well one of the first things to happen is they'll get stuck with a lot more unsold shoes. Lots of people will buy up shoes, then if they can't get them moved in 7 days, just return them. Thats how it used to work. I did it all the time. I once made 20 custom Kobe shoes just to sell, 3 people pulled out, so I just returned them. The Kobe AD Black History month were a custom build, and they're $1,800 now, I wish I'd made a bunch of them. As StockX has grown, Nike has seen more of their shoes across a size run sell out. That'll stop if StockX dies off.