As with 99% of these business threads, all behaviors can be explained by (a) the size of the firm; (b) what the firm principally does; (c) the firm's goals in the gaming space. The big tech companies (I'll include MS here, Apple too, even though especially Apple does in fact also want you to buy their physical products) principally care about stuff like this acquisition entirely outside the gaming space: Amazon, Google, etc. are far more concerned that anti-trust policies particularly in the United States remain largely toothless and even at that unenforced. All those companies are (a) giant; (b) mostly focused on software (I'm excluding everyone's financial services as that's too complicated and everyone but Nintendo does it); (c) want to eventually have a fully digital platform economy for gaming a la TV/film streamlining services. The day MS gets GamePass on every new smart TV, phone, tablet, etc. they're gonna ramp down production and emphasis on Xbox. I wouldn't be surprised if they dumped the (kinda very 90s/00s) Xbox brand altogether in favor of the more neutral "Game Pass" as their gaming division. That's their path; whether it's currently profitable or not is immaterial. As I've pointed out before, Xbox is miniscule to MS; it brings in less revenue and profit than some of the tiniest bits of MS like LinkedIn which costs next to nothing to run and keep up. Apple, Google, Amazon would all like a piece of an eventual streaming market and are more than happy to let MS - Netflix style - lead the way. (I'm glossing genuine antipathy and competition between these firms but no one at Amazon, Google, Apple etc. is under any illusions about overtaking MS in what is basically the MS game (summarized here) in the near or even probably midterm.
On the other end of the spectrum is Nintendo: (a) for a multinational, it's tiny; (b) it is almost exclusively a game and toy maker [I don't mean toys pejoratively here, I just mean that's their lineage and still something the focus on, not just gaming peripherals but think Amiibos for example]; (c) it's goal is longevity, preserving recognition/domination of their existing IP, and selling both hardware and software. Nintendo is not in the big tech arms race really; they are in their own lane almost like pre-2000s Disney. They don't need to sell bleeding edge technology; they know that mass audiences (including many enthusiasts) who already recognize and have investment in their IP are perfectly happy with what they're putting out. They also know they have the handheld market basically locked down (don't really don't with Steam Deck, it's not a mass market device); they also have the sort of minor gaming market (what I mean by this is people who will only spend a moderate amount, want an unobtrusive device, low power draw, etc.) on lock except MS is at least competing there with the Series S. They know that Nintendo games can move their hardware but they can't just put out anything (Wii U) and they do need third party support but are happy for it to be specialty (think MH: Rise, or Octopath being timed exclusives for example) from major companies, or indies (huge PC/Switch pipeline). The Switch ticks all their boxes and I imagine the next Switch will too. CoD doesn't matter to them. If they get a down port or a special version great; if they don't, people who are principally CoD players are almost certainly buying something else or are multiplatform owners.
Stuck in the middle is Sony (and I say this as someone who loves their Playstation and thinks Sony is doing great things.) Sony is (a) a medium sized multinational; (b) it's a hardware company (not just gaming but of course all kinds of consumer electronics, a software company, an entertainment (outside of gaming) company; (c) Sony cannot lose all of its other arms but gaming is if I recall correctly their most profitable and largest share of profit division (again I'm doing from memory and excluding finance although I doubt in Sony's case that's much more than Sony lined credit cards, financing on hardware, etc.); thus their goal is to shockingly to sell hardware, software, and entertainment. Sounds not that tough? BUT Sony needs units to be profitable or at minimum loss whether we're talking hardware or software. They need - and are currently trying to link - all their divisions to push one another (e.g. you want God of War so you get a PS5 but Sony would also like you to be buying TVs, audio gear, that your PS5 is playing on, AND they'd like you to buy a ticket to God of War: the Film - I have no idea if this has been announced, but surely it will - starring, I don't know, the Rock, produced and distributed by Sony pictures. If Sony can thread this needle - which is hard but possible - that's their desired path to profitability. Their size means they have much less wiggle room than MS or big tech companies. Sony cannot afford to be in the streaming platform arms race but are too big / too multifacted to completely 'go their own way' a la Nintendo. Despite a dominant position in the current console market, even the most aggressive minded regulators don't looks at Sony as anything like a monopoly (since it isn't. Also, Nintendo really is close to handheld monopoly but they are so small that no one - in US gov I mean - cares.) So Sony doesn't have that concern; in fact if regulators were to start aggressive enforcement it might be to their advantage. But they are in direct competition in the gaming hardware space and NA/EU software space with MS. So the Activision acquisition, if it turns just a decent small percentage of PS users into Xbox/GP users that can actually hurt Sony quite badly. Now, I actually don't think it will happen too badly. MS might do some kind of timed exclusives or I bet more likely exclusive tie-in content or throw games for free on GP that Sony will have to charge list price for but recall that MS's goal is GP on everything; your phone, your TV, your toaster, doesn't matter, it's gotta have GP on it. At least for the time being, MS has much more to gain from just lightly adding friction to things like CoD than it does by locking out its now leading IP from a massive market.
FWIW, my pure economic reason brain on: MS is likely to get to the goal of Netflix-for-games on everything. If they want it, they have the capital, stability, size, and complementary software domination to make that happen. And Nintendo will continue it's thing (they are almost mercantile in their market approach, even in bad years - cough, again wii u - they're generally stockpiling cash. If it loses everything MS has to offer (which seems unlikely given their current relationship) it is not really affected. For everyone else (but Sony) this is a small potatoes fight until streaming or something very much like it becomes untethered from specific hardware (the MS goal.) For Sony if MS does this they will have to thread the needle above. It remains to be seen if it will work. If not I could imagine Sony spinning off into multiple companies.
FWIW 2: I think Sony is right (even if I don't believe for a second they really care beyond the bottom line) that in the long run GP will be incredibly bad for the quality of particularly single player games. Again Netflix should serves as a guide (and not their current crisis); Spotify is helpful too. As the platforms achieve desired market share, they decrease funding for production (if you think MS gaming will continue generous indie payouts for example once it's like Netflix or Spotify, I have a bridge to sell you) and increase subscription costs for consumers (cause they can.) Think of how Netflix, even before it's current crisis which is somewhat overblown, shifted to just buying up foreign IP and cutting original content short based not even on popularity but on when things like legally dictated or contractually obligated payments are to start. They will also probably (again just business logic) not only stop funding non-MS projects, and under-funding MS projects, but put the most meager payouts (like Spotify) for basically everything. I bet many indie studios can survive by going/returning to PC-only/ PC-Nintendo development but smaller corporate studios are really in a bind in such a situation. You'll see a lot of studios across the board cut even as the appearance of "content" will balloon because you can buy up global production for many years and many indies will still be desperate for the 'exposure'. (Honestly, I wouldn't be surprised to see indie studios turning - as many already are - to pop-music-like methods, merchandising, etc. to make up for lost sales.) But ask any musician or actor and they'll say the same thing; that system is worse than even the old fashioned studio system which was already horrendous.
I really hope people don't take this in a console wars way. I have thought many times about starting a thread devoted just to cold business analysis because almost all non-game (play, criticism, discussion, etc.) threads that get into either business stuff or "why doesn't X company do what Y company does" can be explained through a more detailed version of the above. It's almost never about some kind of better or worse quality of a firm, or some kind of devotion to the medium, etc. It's almost always about firm size, structure, goals, and the short, medium, long term bottom lines.