They sell servers, but as a finished product. Not as a cobbled together mess of third party stuff where the vendor keeps shrugging if there is an integration problem. They integrated it. It comes with all the features they expect you to want if you wanted to build your own cloud.
Also, they wrote the software. And it's all open source. So no "sorry but the third party vendor dropped support for the bios". You get the source code. Even if Oxide goes bust, you can still salvage things in a pinch.
Ironically this looks like the realization of Richard Stallman's dream where users can help each other if something doesn't work.
Proxmox and a full rack of Supermicro gear would not be as sophisticated, but end result is pretty much the same, with I imagine far far better bang for buck.
I like it, but it doesn't seem like a big deal or revolutionary in any way.
I think the question is how well they can do the management plane. Dealing with the "quirks" of a bunch of grey box supermicro stuff is always painful in one way or another. The drop shipped, pre-cabled cab setups are definitely nice but that's only a part of what Oxide is doing here. No cables and their own integrated switching sounds nice too (stuff from the big vendors like UCS is closer to this ballpark but also probably closer to the cost too).
I suspect cooling and rack density could be better in the Oxide solution too, not having to conform to the standards might afford them some possibilities (although that's just a guess, and even if they do improve there these may not be the bottlenecks for many).
Docs:
* https://docs.oxide.computer/api/guides/responses
See perhaps "This repo houses the work-in-progress Oxide Rack control plane."