I think this is a suit to suit trade.
People at MS prospected ActiBliz as something they could buy with all the cash they had (excess of cash). Remember they don't want to have cash but assets.
Back in the day ActiBliz had good assets in form of Human Resources and IP: Starcraft, Warcraft, COD, Diablo, Overwatch, the mobile division, etc.
Also this is a "back to home" ownership move.
They probably started scouting this at 2018-2019. Even earlier.
Bobby has done a great job making the numbers good all this time at expenses of Human Resources.
Look at ActiBliz desparete-moves done quarterly buffing the numbers by consecutive releases to make up financial reports.
Now many people at MS and ActiBliz will get their bonuses, hug, snowwhite-smile and go to Bahamas.
They have traded cash for assets that will bring revenue and profit in the future (ahem). Financially improved MS games division, they have a card against Sony (COD). GeGe.
Future? In the next 3-5 years probably nobody regarding this trade will still be at MS.
People will blame the MS Gaming pass integration for the failure of monetization of the IPs of Actiblizz (except COD) and, exept for the mass labour layoffs due to AI and market status of course, nobody will care.
MS game pass (or any other pass) is not about having good games, is about having as much people as possible pay each month. You do that by adding new "posters" to the collection. If a game is played for a month or two is fine as long as you keep retention. You may, statistically, have good games from time to time of course.