Elder Scrolls, Fallout, and Doom were the big IP gains. Bethesda and Id Software were the big studio gains. Nothing else they acquired is that big of a deal, to be honest.
For IPs, no one knows anything about Starfield nevermind getting attached to it as a franchise. Wolfenstein, Prey, Dishonored, and Evil Within are not anything that would make a big difference. We're even assuming that Prey, Dishonored, and Evil Within are going to continue at all.
For studios? Alpha Dog is just a small mobile developer that I would be surprised survives the acquisition. Roundhouse is the old Human Head team and quite frankly they suck. ZeniMax Online made one MMO themselves that they had to make free-to-play to survive and it's already on PS5. If they ever make another game it will likely be a long time from now and risky. Tango Gameworks isn't bad but they're not headliners and Arkane's titles always seem to be flashes in the pan. Machine Games did great with Wolfenstein 2 but their entries before that weren't nearly as good and Youngblood, which they developed alongside Arkane, was terrible.
Hell, Bethesda itself has been shoddy lately. They had a streak of great, if not fantastic games, for a long time with Fallout 4 being the end of that streak 6 years ago. Fallout 76 was dogshit and Elder Scrolls: Blades impressed no one. Hopefully they get their shit together under Microsoft because I'm really hoping Elder Scrolls 6 is awesome. But if nothing else Id Software is on fire with Doom with right now so that will further cement Microsoft in the FPS genre which Sony has pretty much abandoned.
Across 5 platforms and over the course of 5 years by the time those numbers were announced. At launch, almost 60% of copies sold were on Xbox. Less than 2 months later, Steam accounted for half of its sales. Comments made over the years make it pretty clear, Skyrim was a wild success on PC. Even crushing Team Fortress 2 and becoming the most played game on Steam by a huge margin. Which was a giant accomplishment at the time. Todd Howard was even quoted as saying that the PC mods are what helped Skyrim blow up. So a logical conclusion is that when it comes to consoles, Xbox was the lead platform for Skyrim anyways. Overall, PC is where Skyrim truly flourished.
Ultimately, it's going to take a long time for Microsoft to bear fruit from this acquisition in the form of exclusives for Xbox. Which assumes they even go that route based on past comments prior to the acquisition going through. Right now there are too many contractual obligations and projects in too early of development for this to have any effect in the first half of this generation. By the time the second half rolls around, which is when you'll start seeing the real results of this acquisition, the generation will have already been decided one way or the other. As I've said in other threads, acquiring ZeniMax will have a far greater impact on future generations than the current one. Though that will be based on whether or not Microsoft's first party can succeed in being competitive with Sony's and Nintendo's. Microsoft has a long ways to go to claw itself out of the distant third place it's in.