It's not really the same. For one, when those were the two juggernauts in the game cartridge era, they weren't really in the business of just scooping up a bunch of game studios, because financially it didn't make much sense.
What's different now is that Microsoft is focusing on becoming the Amazon Prime Video of video games. While you will still be able to buy the games outright, the games of the companies they're purchasing will be part of the monthly price gamers pay to play.
So for instance, because they own Zenimax, I can load up any of the Bethesda / id games and play as part of my subscription. And when Starfield and Elder Scrolls VI come out, they'll be part of that price too. Buying Activision brings Call of Duty, Overwatch, Warcraft, Starcraft, Diablo, and a host of other games under the same umbrella.
I guess they've decided that low monthly subscriptions paired with season passes for content is the way of the future for gaming.