Here's how I see it.
MS buying up big studios is more about filling their already existing studios that lack talent. I don't think MS wants to control or create a monopoly in the gaming industry. When you look at the actual content for MS, they are lacking in popularity of their own IPs. They literally have no choice but to buy up the studios that garner the best sales and the largest influence across the gaming industry. It's more of a defensive move imo due to the lack of popularity. They got an excellent deal with buying Asobo Studios because that's one of those talented companies that rivals a Sony-based studio.
Sony doesn't have the resources to buy large studios like that and to me, they shouldn't buy them even if they had the money. Sony basically has most of the talent in the industry and MS could be looking at that as a monopoly (even though it's not).
Let the Xbox fans enjoy their new studios. The Sony fans do it ad infinity as they have some of the best talent in the industry and nearly all their studios make GOTY content.
There's no need for either camp to be frustrated with each other. We can all talk about this in peace without bashing each other down for 'routing for the cause'.
Lastly, of course it's all about money and investors. Both companies (like every other company) wants to make money. Having the best studios, or the best talent or the most sales, etc.. all contributes to making more money. At the end of the day, let's not pretend that it's not about that.
Even if Sony had the means, it's not in their nature to buy something as large as Acitivsino/Blizzard mainly because of how they internally run things when it comes to studios.
Thats why Bungie is being left alone, it makes no sense for Sony to try and change a self made studio thats been on their own.
Every purchase Sony has made for the most part was never when a studio was in dire straits, or not doing well. Insomniac was fine money wise, but wanted to sell because they wanted to grow and have more assurances of said growth.
Which you do that through a larger company.
Microsoft is literally buying a Publisher. Take Call of Duty out of the talking point, and you are left still with the second largest Tech giant buying the biggest to second largest Third party publisher in the gaming sector.
The ripple effects it will have would be enormous to the revenue streams generated from it. THink retail? Think midnight launches, and retailers that actually make a good amount off of releases like COD.
Think of companies who sell their headsets, peripherals literally based on COD releases. If tomorrow COD became exclusive the implications of it would have negative effects.
The same goes for WOW and Diablo brand wise. PC companies that make keyboards/Mice/Headsets and gaming gear would be affected if WOW was pulled and walled off.
So assurances need to be made. Thats what this is all about. It's not about stopping it, its about having assurances in place that will insure companies wont lose those revenue streams created by those releases.