msft is acquiring both horizontally (compared to their existing inhouse studios - notably their previous acquisition of zenimax/bethesda) and vertically (as activision/blizzard/king are the biggest developer of games for xbox and playstation).
the plan is 2 fold: 1. short term - instead of competing with sony on securing exclusivity, ensure exclusivity by ownership 2. long term - bolster xbox cloud gaming by ensuring that every major game exists on the platform (ideally exclusively)
the idea is that once you have a suprior catalog of games and a working subscription platform, you can boil your customers like frogs via price increases / ads / etc and that they will have no where to go because the games they want to play are exclusive to your service. with this acquisition msft is acquiring some of the most valuable ip in gaming, the development talent behind that api, and the audiences and communities that power it all and locking them down to xbox cloud gaming.
It may still be true that cloud gaming is not an interesting product, but google’s failure to enter it isn’t proof of that.
That’s how you dominate “cloud” gaming— it becomes the only option you give customers to purchase games.
Also, fewer competitors leads to a less interesting market. Imagine the NFL with just 4 teams.
As far as Microsoft/Activision goes, it's potentially a good thing, but just because Activision was also made of acquisitions and drive for profit came at the cost of lower quality of their releases, IMO. Microsoft might reinvigorate Activision/Blizzard's IP.
In terms of vendors, consolidation is like a black hole. The more consolidation, the bigger the black hole and the more vendors crushed by the gravity.
The company will do meaningful work, have better pricing, and employees will have more customer focus and less office politics.