The reason one off deals are not scrutinised by regulators is because it's 2 independent parties acting with separate best interests who regulators cannot tell what to do. Want to spend $75M to secure GTA4 dlc? You are pumping money into the industry and the third party can use it to fund GTA5 for all competitors. Want to go fund SF5? fine you are pumping money into an independent company for the development of SF6. It's third parties acting in their own best interest. Start buy all the publishers and IP though and you are pumping money into yourself, it's the self interest of one entity to the detriment of competition. Cartels operate in the same fashion even though independent. Consumers may not like either buyouts or third party moneyhats but at least the latter is an independent vertical company with self serving interests at the end of the day. One which doesn't stop competition making whatever offers between other parties.
The CMA have used internal documents from MS, ABK, and third parties for cloud gaming and multigame subscriptions. It's the companies themselves saying they are going to succeed with cloud and multigame subs overtaking consoles.
As for pricing benefits. The CMA are absolutely
for pricing benefits but pricing benefit can have bad intentions which is what they look at. Predatory pricing is another 'pricing benefit' but it benefits nobody. The CMA saw internal MS documents that there is a possible foreclosure strategy, most of them redacted unfortunately. It could be as simple as increasing prices once the competition is not competitive anymore.
For the time period this looks at, that's a little more murky. I suspect "long term" is for whatever period the projections would still hold statistically outside of unpredicted market disruptors.
I commend the regulators for looking at every aspect of the industry cloud, subs, console and the fact that they have even brought up OS is amazing. I still maintain that a console future with Steam Machines failed mostly due
to SteamOS not being competitive back then. The consoles were capable of running games like COD and FIFA but couldn't officially. A console that couldn't play most games even though it was technically capable. They had less then 10% game compatibility with their own walled garden store. the alternative was to go buy a windows license. It completely killed its chances as a price competitive easy to use console.