I'd say it is because the $ it takes to build out even a small gpu data center is still way, way more than most small cos can do. It's not an impenetrable moat, but it is pretty insulating against startups. Still have a threat from big tech, though I think that will always be true for almost everything
I don't think the hardware is that easy to source just yet. Musk pulled some strings and redirected existing inventory and orders from his other companies, namely Tesla, to accelerate delivery.
xAI does not have infra to sell the service and integrations of it to enterprises and such. It's an open question if "models" alone and simple consumer products that use them are profitable. So, probably hyperscale cloud platform infra is a moat yes. Microsoft has Semantic Kernel, Microsoft.Extensions.AI, various RAG and search services, and an entire ecosystem and platform around using LLM's to build with that xAI does not have. Just having a chat app as interface to one's model is part of the discussion here about models as commodities. xAI does have X/Twitter data which is a constantly updating source of information so in that aspect they themselves do have something unique.