For now. Fortunes change pretty quick in the console world. One generation you are on top, the next you are struggling for second place.
MS buying Activision is bad. This gives MS a long term advantage. It signals to companies like Sony and Nintendo that they shouldn’t bother competing since they can never counter the buying out of huge publishers as they aren’t worth 2.47 trillion USD like Microsoft.
Has Microsoft has any major successes since Halo and Fable, years and years ago? They're desperate for games. Activision isn't going to suddenly make the dominant overnight. If anything, it would barely help stop the bleeding. Microsoft is so far behind right now it's not funny. I'd be way more afraid of competition dying because Microsoft gave up on it rather than buying Activision.
3rd party support plays a big part in a console’s success. MS is effectively buying out one of the largest 3rd party studios denying its competitors their support.
Buying up one of the biggest publishers though. What’s Sony and Nintendo, whose combined market cap is less than 7% of MS’s, suppose to do? I don’t see how allowing “big money Pay 2 Win without a fight” in anyway benefits the consumer.
How much of that MC is solely X-box and how much do MS , Sony, and Nintendo own of that respectively? MS studios has been struggling. Activision also has been struggling to land some hits and only recently with Diablo 4 they have got some relief. So buying Activision is not a golden ticket.