These clauses exist to
protect the seller, not the buyer. As a company under acquisition you are massively limited in how you can operate, trade, or acquire and expand yourself. The clauses provide protection that the buyer isn't going to jerk your company around and you're not left in regulatory purgatory for months/years, which is why the $3b delay penalty kicks in at midnight is Microsoft don't close, which they can't.
These clauses are common in large acquisitions, you may remember Elon Musk tried to back out of his Twitter acquisition but the cost was going to be so massive, he was forced into buying it. He is now trying to
sue the lawyers who enforced that clause because despite his genius, he's also a moron.
This delay works well for Activision-Blizzard shareholders because they'll effectively get an extra $3.2 dollar increase per share as a result. But let's not foregt that the CMA are not the last regulator needing to provide approval;
New Zealand is still assessing, as are
Australia, and the Canadian regulator said they were "monitoring it" given some revelations in the FTC case seeming contradiction evidence provided to them, although they've said nothing since.
Microsoft keep saying it's only the CMA holding up the close, but it's not.
Perhaps Microsoft don't care about Australia and New Zealand ¯\_(ツ)_/¯