It’s not clear what happened with the Sega acquisition and whether Nadella ultimately approved talks. But in a Microsoft internal April 2021 merger review document, Sega was still listed as a key target. Microsoft had identified key areas for acquisitions in PC, mobile, and console across different markets, and Sega, Bungie, Zynga, and IO Interactive were part of a number of companies Microsoft was seriously looking at acquiring.
Microsoft out here treating studios like most of us treat new games on Steam. Acquire them and then never do anything with them.