Why would it need more than 1? Couldn't they do this with any Mac with an Apple account?
Mac Minis are perfect for locally running demanding models because they can effectively use ordinary RAM as VRAM.
Considering there are 1.5M openclaw agents, created by 17,000 humans, it seems like some people really would use more than 1.
There are few open source projects coming along that let you sell your compute power in a decentralized way. I don't know how genuine some of these are [0] but it could be the reason: people are just trying to make money.
It appears he is selling a service where he comes to you (optionally with a Mac Mini which is probably why he's buying multiple) and sets up OpenClaw for you.