It will likely never be a true monopoly. But an oligopoly with two or three players? That's where we are and where we'll remain.
Its the only serious use case for enterprise.
What, you want to use azure?
I worked at Amazon for over 5 years and I currently work for a pretty big company (you've heard of them) that's all-in on Azure. It's got enough going for it that I wouldn't switch even if I were high enough in the hierarchy to make that decision.
GCP, Azure, Oracle, Alibaba ... just to name a few.