Microsoft already owns a large number of successful studios and IP, such as Halo, Minecraft, and Bethesda, developers of The Elder Scrolls Series (Skyrim) and the upcoming Starfield. They don't need a helping hand from the government to prevent them being squished out. Starfield was confirmed to have been going on Playstation until they were acquired by Microsoft; now the only way to play it will be on Xbox or Windows.

If Microsoft buys Activision/Blizzard, it's safe to assume that future A/B games will go the same way, and only be available on Xbox or Windows. This is problematic because Activision's IP portfolio is massive (including huge console annuals like Call of Duty), and Blizzard games are still extremely popular. If a normal game studio acquisition is like a comet colliding and adding its mass to the Earth, this would be like the moon crashing into the Earth.