If you had to bet on which of this year’s big tech acquisitions would fall apart, you might have thought the obvious choice was Twitter-Musk, at least before Tuesday’s news that Musk has reversed course and is willing to close. (And even now the completion of that deal isn’t certain.) But arguably a more likely candidate for deal implosion was always Microsoft’s $68.7 billion proposed acquisition of Activision. After all, the only issue for the Twitter deal was Musk’s capriciousness, and this week’s developments suggest even he has realized he doesn’t have a leg to stand on in trying to get out of the transaction.

But Microsoft’s deal faces tough regulatory reviews in both the U.S. and Europe, which are understandable given the company’s size and its sizable share of the gaming market courtesy of the Xbox. Investors certainly seem doubtful about the deal’s prospects, judging by how much they’re paying for Activision right now—nearly $21 below the $95 offer price. I hear that the community of arbitrageurs, those wily traders who bet on whether announced deals will actually close, have bigger positions in Twitter than in Activision—suggesting they had greater confidence in Twitter closing even before this week. If regulators succeeded in blocking the Microsoft deal, it would be a stunning blow for the aging tech giant, which in recent years has done a spate of acquisitions seemingly without an antitrust care in the world. That’s in stark contrast to the experience of other big tech companies like Alphabet, Meta Platforms and Amazon.