British antitrust regulators dealt a major setback on Wednesday to Microsoft's plans to acquire the video game giant Activision Blizzard for $69 billion, blocking the proposed deal and handing a notable win to government enforcers around the world who want to rein in Big Tech.

Activision's stock fell 11 percent by the close of trading. Shares of Microsoft, which were trading higher after it reported stronger-than-expected earnings on Tuesday, rose 7 percent on Wednesday.

Can you provide an explanation for why Activision's stock fell but Microsoft's rose after the ruling by British antitrust regulators?