Also the when of consuming content.
Let's make an example to illustrate: Ordinarily, the holiday season would see releases from various big publishers, you would see Activision releasing COD, Microsoft releasing their new Halo games, Bethesda releasing DOOM or Fallout etc.
Now if both Bethesda and Activision are under MS, then all their IP is now impacting a single ROI, rather than multiple competing ones, meaning that MS will most definitely have to reduce the amount of games they release every month, both to ensure "cadence" for Gamepass/XBox as a whole, and to limit self-cannibalization of the consumer dollars that change hands in said season. This essentially means they can't release a Doom and a COD together in the same launch window, because there is intersection in their appeal, and one will invariably cannibalize the other leading to limited full-price sales (i.e. a customer will likely buy one immediately, and wait for the other to drop price), this is a direct example of how these big corpo mergers directly affect the consumer's choice, and it's relatively platform-agnostic (as in it doesn't really matter if both franchises are released on PS5 or Switch, the commercial decision will likely remain the same).
Big mergers are a major waste of resources that could go to appeasing the consumer (just think how many brand-new high-quality AAA franchises could be funded with 70b, all additive to the gaming space and pushing the craft forward), they also reduce the choice of consumers across multiple axes as well.
