Sony doesn’t have anything close to the scale of Azure and they don’t have the rest of the business model as a backstop to cover the cost of their gaming services.
Google doesn’t have a major gaming brand like Xbox and doesn’t own any publishers - Microsoft has Microsoft Studios and Zenimax already.
NVIDIA same thing they have the hardware business on their side but they don’t have a cloud like Azure, GCP or AWS nor do they have gaming IP in their pocket.
Again the issue is you are looking at this problem from the perspective of today and by taking into account only individual elements.
What the CMA is looking at is Xbox Brand + 70% of the current market + 2nd largest CSP with datacenters all over the globe and the ability to share the cost across other profitable offerings + Being the 3rd largest publisher and owning a fuck ton of gaming IP.
Now extrapolate 5, 10 and 20 years down from that staring point.
And remember you can always make an argument what if Google or NVIDIA invest every last cent they have to give Microsoft a run for their money but you can also make a counter argument what if Microsoft does the same.
In that case Microsoft still is in a far better position because of their current position in the market.
But when you extrapolate more realistically based on existing business models and ventures as well as the actual cost of developing these services further Microsoft is in a very strong position already and possibly the strongest of all players. Making them even stronger is exactly what regulators like the CMA are here to prevent.