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.