OpenAI doesn’t operate without the enormous amounts of funding MS gives it.
If MS drops OpenAI, it's not like they can just seamlessly pivot to running their own data centers with no downtime, even with pretty high investment.
I’d note that the supplier of GPUs is Nvidia, who also offers cloud GPU services and doesn’t have a stake in the GCP, Azure, AWS behemoth battle. I’d actually see that as a more natural less middle man relationship.
The real value azure brings is enterprise compliance chops. However IMO aws bedrock seems to be a more successful enterprise integration point. But they’re all commodity products and don’t provide the value OpenAI provides to the relationships.