My theory:
Microsoft is buying these studios to put itself in a position where one day Sony and Nintendo feel pressure to allow Gamepass on their devices or risk losing out on tremendous amounts of games. The more they buy the more pressure there is, and then MS collects fat checks on not only Xboxes/PCs, but also PlayStations and Nintendo devices. They have already done a tremendous amount of work at consolidating Western studios to apply this pressure, are working on deals with massive studios they can't buy (EA and Ubisoft, rumor has it) to have their games added to Gamepass (even if just some), and are now working on Japanese developers to really up the pressure on them. Getting these two studios wouldn't enable Xbox to have success in Japan, but if my theory is right it will enable Microsoft to have success in Japan by forcing Gamepass unto Switch 1 or 2 and PS5.
At some point, Nintendo and Sony won't be able to simply accept loss of access to a huge, seemingly-ever-growing-amount of games (since MS is buying so many) and they will have to bite the bullet and allow Gamepass on their devices or risk having lower software/hardware sales than necessary to make their respective consoles profitable enough to appease shareholders.