Why is buying 1 studio monopolistic?
I have been gaming for decades and I've never felt the need to play games from every studio.
Heck, large studios are mostly a negative in the modern era. They have the resources to use microtransactions and DRM. Meanwhile indie games have to try their best to get any attention.
Even if M$ bought every studio in existence, PlayStation and Nintendo, there would still be indie games in a few years. Not to mention uncountable number of games from the last few decades that is enough entertainment to last you a few lifetimes.