Yes in a complete hypothetical scenario anything could become a monopoly but those aren’t the facts we have or the reality we live in.

The point that the CMA made is that the combined advantages that Microsoft has already with this acquisition will position it well ahead of the competition to the point where it will get a natural monopoly. Natural monopolies are still monopolies even if no one else right now wants to compete.

This is literally what regulators like the CMA are here for.