Amazon and Google aren't throwing around their weight like Microsoft is though. I'm sure part of the reason for this deal is to avoid one of those players from entering the game by buying one of the few big publishers. A lot of Microsoft's moves these past several years have definitely been to stave off potential efforts from companies the size of Google, Amazon, or Apple rather than competing with Sony or Nintendo. I think the three of Microsoft, Sony, and Nintendo are quite comfortable in their niche but I don't think its an accident that all this is happening after big pushes from companies like Amazon, Google, Facebook and Apple.When we're talking about market share, Microsoft being the parent company absolutely has no bearing. You cant just shrug off Sony nearing 50%+ market share in the console space with "but Microsoft is a bigger company", thats silly.
The same reason we wouldn't say Stadia and Luna are bigger than PlayStation.
I think being too laser focused on the console gaming niche makes you lose focus on the bigger picture. You see something like Stadia bombing and write of Google but I think Microsoft was definitely wary of it (and similar projects) and future attempts.